View source for SARS-CoV-2 Omicron variant

{{Short description|Type of the virus first detected in November 2021}}
{{Use dmy dates|date=September 2024}}
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{{Main article|Variants of SARS-CoV-2}}
{{anchor|BA.2.3.20|BF.7|BJ.1|BM.1.1.1|BQ.1.2|BQ.1.3|BQ.1.4.2}}<!-- parked anchors for Omicron variants with incoming links but not yet discussed explicitly inhere -->
{{Infobox SARS-CoV-2 Variant
| variant = Omicron
| status = [[Variant of concern]]
| dateReported = {{start date and age|2021|11|24|df=y}}
| reportedLocation = [[South Africa]]
| lineage = B.1.1.529
| omicron = yes
| hidemap = yes
| symptoms = [[Asymptomatic infection]],<ref name="Yadav2022">{{Cite conference |pages=2022–01.02.474750 |vauthors=Yadav PD, Gupta N, Potdar V, Mohandas S, Sahay RR, Sarkale P, Shete AM, Razdan A, Patil DY, Nyayanit DA, Joshi Y |title=An in vitro and in vivo approach for the isolation of Omicron variant from human clinical specimens |access-date=16 January 2022 |date=January 2022 |doi=10.1101/2022.01.02.474750 |url=https://www.biorxiv.org/content/10.1101/2022.01.02.474750v1 |conference= |archive-date=16 January 2022 |archive-url=https://web.archive.org/web/20220116120738/https://www.biorxiv.org/content/10.1101/2022.01.02.474750v1 |url-status=live}}</ref> [[body ache]],<ref name="Yadav2022" /> [[cough]],<ref name="Yadav2022" /> [[fainting]],<ref name="Malvika">{{cite news |vauthors=Padin M |title=Feeling light-headed may be an early indication you have Omicron Covid variant |url=https://www.mirror.co.uk/news/uk-news/fainting-spells-could-covid-warning-25967128 |work=[[Daily Mirror]] |date=17 January 2022 |access-date=30 January 2022 |archive-date=28 January 2022 |archive-url=https://web.archive.org/web/20220128123815/https://www.mirror.co.uk/news/uk-news/fainting-spells-could-covid-warning-25967128 |url-status=live}}</ref> [[fatigue]],<ref name="Poudel2022">{{cite journal |vauthors=Poudel S, Ishak A, Perez-Fernandez J, Garcia E, León-Figueroa DA, Romaní L, Bonilla-Aldana DK, Rodriguez-Morales AJ |title=Highly mutated SARS-CoV-2 Omicron variant sparks significant concern among global experts – What is known so far? |journal=Travel Medicine and Infectious Disease |volume=45 |page=102234 |date=December 2021 |pmid=34896326 |pmc=8666662 |doi=10.1016/j.tmaid.2021.102234}}</ref> [[fever]], [[headache]],<ref name="guardian2021" /> [[Anosmia|loss of smell]] or [[Ageusia|taste]],<ref name="nbcchicago2723960" /><ref name="metro.co.uk15967386" /> — less common
[[nasal congestion]] or [[running nose]]<ref name="guardian2021">{{cite web |vauthors=Adams R |url=https://www.theguardian.com/world/2021/dec/24/omicron-covid-symptoms-uk-guidance-zoe-study |url-status=live |date=24 December 2021 |title=Omicron's cold-like symptoms mean UK guidance 'needs urgent update' |archive-url=https://web.archive.org/web/20211225032402/https://www.theguardian.com/world/2021/dec/24/omicron-covid-symptoms-uk-guidance-zoe-study |archive-date=25 December 2021 |newspaper=[[The Guardian]] }}</ref> [[night sweats]],<ref name="Scribner2021">{{Cite web| vauthors = Scribner H |date=21 December 2021|title=Doctor reveals new nightly omicron variant symptom|url=https://www.deseret.com/coronavirus/2021/12/21/22847247/new-omicron-variant-symptom-night-sweats-sweating-covid|access-date=1 January 2022|website=Deseret News|archive-date=2 January 2022|archive-url=https://web.archive.org/web/20220102140417/https://www.deseret.com/coronavirus/2021/12/21/22847247/new-omicron-variant-symptom-night-sweats-sweating-covid|url-status=live}}</ref> — unique Omicron symptom, upper [[respiratory tract infection]]<ref>{{cite news |title=Does Omicron cause less damage to the lungs? |url=https://www.medicalnewstoday.com/articles/covid-19-does-omicron-cause-less-damage-to-the-lungs |work=medicalnewstoday.com |date=14 January 2022 |access-date=22 August 2023 |archive-date=9 February 2022 |archive-url=https://web.archive.org/web/20220209215147/https://www.medicalnewstoday.com/articles/covid-19-does-omicron-cause-less-damage-to-the-lungs |url-status=live }}</ref> [[skin rash]],<ref>{{cite news | vauthors = Murrison P |title=Omicron symptoms: Three distinctive rashes to watch for |url=https://www.express.co.uk/life-style/health/1547779/omicron-symptoms-rash-type-skin-itchy-evg |work=Express.co.uk |date=18 January 2022 |access-date=30 January 2022 |archive-date=12 January 2022 |archive-url=https://web.archive.org/web/20220112062133/https://www.express.co.uk/life-style/health/1547779/omicron-symptoms-rash-type-skin-itchy-evg |url-status=live }}</ref> [[sneezing]],<ref name="guardian2021"/> [[sore throat]]<ref name="Malvika" />
}}
'''Omicron''' (B.1.1.529) is a [[Variants of SARS-CoV-2|variant of SARS-CoV-2]] first reported to the [[World Health Organization]] (WHO) by the Network for Genomics Surveillance in South Africa on 24 November 2021.<ref name=":0b">{{cite journal |vauthors=Quarleri J, Galvan V, Delpino MV |title=Omicron variant of the SARS-CoV-2: a quest to define the consequences of its high mutational load |journal=GeroScience |volume=44 |issue=1 |pages=53–56 |date=February 2022 |pmid=34921354 |pmc=8683309 |doi=10.1007/s11357-021-00500-4}}</ref><ref name="Gowrisankar2022">{{cite journal |vauthors=Gowrisankar A, Priyanka TM, Banerjee S |title=Omicron: a mysterious variant of concern |journal=European Physical Journal Plus |volume=137 |issue=1 |page=100 |date=10 January 2022 |pmid=35036269 |pmc=8743750 |doi=10.1140/epjp/s13360-021-02321-y |bibcode=2022EPJP..137..100G}}</ref> It was first detected in [[Botswana]] and has spread to become the predominant variant in circulation around the world.<ref name=":0a">{{cite journal |vauthors=Vitiello A, Ferrara F, Auti AM, Di Domenico M, Boccellino M |title=Advances in the Omicron variant development |journal=Journal of Internal Medicine |volume=292 |issue=1 |pages=81–90 |date=July 2022 |pmid=35289434 |pmc=9115048 |doi=10.1111/joim.13478}}</ref> Following the original B.1.1.529 variant, several subvariants of Omicron have emerged including: [[BA.1]], [[BA.2]], [[BA.3]], [[BA.4]], and [[BA.5]].<ref name=":1a">{{cite journal |vauthors=Yao L, Zhu KL, Jiang XL, Wang XJ, Zhan BD, Gao HX, Geng XY, Duan LJ, Dai EH, Ma MJ |title=Omicron subvariants escape antibodies elicited by vaccination and BA.2.2 infection |journal=The Lancet. Infectious Diseases |date=June 2022 |volume=22 |issue=8 |pages=1116–1117 |pmid=35738299 |pmc=9212811 |doi=10.1016/s1473-3099(22)00410-8}}</ref> Since October 2022, two subvariants of BA.5 called [[BQ.1]] and [[BQ.1.1]] have emerged.

As of September 28, 2024, a new subvariant  of Omicron labeled XEC has emerged. The new variant is found in Europe, and in 25 states in the United States of America, including three cases in California.<ref>{{Cite web |title=New XEC Covid variant: What are the symptoms and is it spreading in the UK? |url=https://www.bbc.com/news/articles/c1jddenj5p5o |access-date=2024-09-26 |website=www.bbc.com |language=en-GB}}</ref>

Three doses of a [[COVID-19 vaccine]] provide protection against severe disease and hospitalisation caused by Omicron and its subvariants.<ref name="Ahmed2022">{{cite journal | vauthors = Ahmed SF, Quadeer AA, McKay MR | title = SARS-CoV-2 T Cell Responses Elicited by COVID-19 Vaccines or Infection Are Expected to Remain Robust against Omicron | journal = Viruses | volume = 14 | issue = 1 | page = 79 | date = January 2022 | pmid = 35062283 | pmc = 8781795 | doi = 10.3390/v14010079 | doi-access = free | title-link = doi }}</ref><ref name="Jurdi2022">{{Cite medRxiv |vauthors=Al Jurdi A, Gassen RB, Borges TJ, Lape IT, Morena L, Efe O, Solhjou Z, El Fekih R, Deban C, Bohan B, Pattanayak V, Kotton CN, Azzi JR, Riella LV |title=Suboptimal antibody response against SARS-CoV-2 Omicron variant after third dose of mRNA vaccine in kidney transplant recipients |pages=1282–1286 |date=June 2022 |medrxiv=10.1101/2022.01.03.22268649v1}}</ref><ref name=":1b">{{cite journal | vauthors = Altarawneh HN, Chemaitelly H, Ayoub HH, Tang P, Hasan MR, Yassine HM, Al-Khatib HA, Smatti MK, Coyle P, Al-Kanaani Z, Al-Kuwari E, Jeremijenko A, Kaleeckal AH, Latif AN, Shaik RM, Abdul-Rahim HF, Nasrallah GK, Al-Kuwari MG, Butt AA, Al-Romaihi HE, Al-Thani MH, Al-Khal A, Bertollini R, Abu-Raddad LJ | title = Effects of Previous Infection and Vaccination on Symptomatic Omicron Infections | journal = The New England Journal of Medicine | volume = 387 | issue = 1 | pages = 21–34 | date = July 2022 | pmid = 35704396 | doi = 10.1056/NEJMoa2203965 | pmc = 9258753 | s2cid = 249677809 }}</ref><ref>{{cite journal | vauthors = Nemet I, Kliker L, Lustig Y, Zuckerman N, Erster O, Cohen C, Kreiss Y, Alroy-Preis S, Regev-Yochay G, Mendelson E, Mandelboim M | title = Third BNT162b2 Vaccination Neutralization of SARS-CoV-2 Omicron Infection | journal = The New England Journal of Medicine | volume = 386 | issue = 5 | pages = 492–494 | date = February 2022 | pmid = 34965337 | pmc = 8823651 | doi = 10.1056/NEJMc2119358 }}</ref> For three-dose vaccinated individuals, the BA.4 and BA.5 variants are more infectious than previous subvariants but there is no evidence of greater sickness or severity.<ref name=":1a" /><ref>{{cite journal | vauthors = Cao Y, Yisimayi A, Jian F, Song W, Xiao T, Wang L, Du S, Wang J, Li Q, Chen X, Yu Y, Wang P, Zhang Z, Liu P, An R, Hao X, Wang Y, Wang J, Feng R, Sun H, Zhao L, Zhang W, Zhao D, Zheng J, Yu L, Li C, Zhang N, Wang R, Niu X, Yang S, Song X, Chai Y, Hu Y, Shi Y, Zheng L, Li Z, Gu Q, Shao F, Huang W, Jin R, Shen Z, Wang Y, Wang X, Xiao J, Xie XS | title = BA.2.12.1, BA.4 and BA.5 escape antibodies elicited by Omicron infection | journal = Nature | pages = 593–602 | date = June 2022 | volume = 608 | issue = 7923 | pmid = 35714668 | doi = 10.1038/s41586-022-04980-y | pmc = 9385493 | bibcode = 2022Natur.608..593C }}</ref><ref>{{cite journal | vauthors = Hachmann NP, Miller J, Collier AY, Ventura JD, Yu J, Rowe M, Bondzie EA, Powers O, Surve N, Hall K, Barouch DH | title = Neutralization Escape by SARS-CoV-2 Omicron Subvariants BA.2.12.1, BA.4, and BA.5 | journal = The New England Journal of Medicine | volume = 387 | issue = 1 | pages = 86–88 | date = July 2022 | pmid = 35731894 | doi = 10.1056/NEJMc2206576 | pmc = 9258748 | s2cid = 249956777 }}</ref>

{{excerpt|Variants of SARS-CoV-2|only=paragraphs|paragraph=2|hat=no}}<!-- This paragraph can be updated in 'Variants of SARS-CoV-2' -->

== Classification ==
[[File:Omicron SARS-CoV-2 radial distance tree 2021-Dec-01.svg|thumb|Omicron variant and other major or previous [[Variant of concern|variants of concern]] of [[Severe acute respiratory syndrome coronavirus 2|SARS-CoV-2]] depicted in a tree scaled radially by genetic distance, derived from [[Nextstrain]] on 1 December 2021]]
{{COVID-19 pandemic sidebar|expanded=}}

On 26 November 2021, the [[World Health Organization|WHO]]'s Technical Advisory Group on SARS-CoV-2 Virus Evolution declared [[PANGOLIN|PANGO lineage]] B.1.1.529 a variant of concern and designated it with the [[Greek letter]] [[omicron]].<ref name=":0b" /> The WHO skipped the preceding letters [[Nu (letter)|nu]] and [[Xi (letter)|xi]] in the [[Greek alphabet]] to avoid confusion with the similarities of the English word "new" and the Chinese surname [[Xi (surname)|Xi]].<ref>{{Cite news| vauthors = Patel V |date=27 November 2021|title=How Omicron, the New Covid-19 Variant, Got Its Name|work=The New York Times|url=https://www.nytimes.com/2021/11/27/world/africa/omicron-covid-greek-alphabet.html|access-date=28 November 2021|issn=0362-4331|archive-date=28 November 2021|archive-url=https://web.archive.org/web/20211128015620/https://www.nytimes.com/2021/11/27/world/africa/omicron-covid-greek-alphabet.html|url-status=live}}</ref>

The name of the variant has occasionally been mistaken as "Omnicron" among some English speakers, due to a lack of familiarity with the [[Greek language|Greek]] alphabet, and the relative frequency of the [[Latin]] prefix "[[wikt:omni-|omni]]" in other common speech.<ref name=Tcholakian>{{cite news |vauthors=Tcholakian D |date=15 December 2021 |title='Omni is everywhere': why do so many people struggle to say Omicron? |url=https://www.theguardian.com/science/2021/dec/15/why-do-so-many-people-struggle-to-say-omicron |url-status=live |access-date=23 December 2021 |website=[[The Guardian]] |archive-date=23 December 2021 |archive-url=https://web.archive.org/web/20211223233517/https://www.theguardian.com/science/2021/dec/15/why-do-so-many-people-struggle-to-say-omicron}}</ref><ref name=Zimmer>{{cite news |vauthors=Zimmer B |date=2 December 2021 |title='Omicron': Greek's 'Little O' Will Loom Larger Now |work=[[Wall Street Journal]] |url=https://www.wsj.com/articles/omicron-greeks-little-o-will-loom-larger-now-11638485846 |url-status=live |access-date=23 December 2021 |issn=0099-9660 |archive-url=https://web.archive.org/web/20211203002839/https://www.wsj.com/articles/omicron-greeks-little-o-will-loom-larger-now-11638485846 |archive-date=3 December 2021 |quote=President Joe Biden stumbled over the pronunciation in a press conference on Monday, calling the variant "omnicron" with an extra "n" sound. It has also been frequently misspelled that way online. The confusion is understandable, since we're more familiar with words that have the Latin prefix "omni-" meaning "all," as in "omnipresent" or "omnivore."}}</ref>

The [[GISAID]] project has assigned it the [[clade]] identifier GR/484A,<ref>{{cite web |url=https://www.gisaid.org/ |title=In focus |author=<!--Not stated--> |date=28 November 2021 |website=gisaid.org |publisher=GISAID |access-date=28 November 2021 |quote=The unique mix of spike amino acid changes in Omicron GR/484A (B.1.1.529) is of interest as it comprises several that were previously known to affect receptor binding and antibody escape. |archive-date=21 January 2021 |archive-url=https://web.archive.org/web/20210121135255/https://www.gisaid.org/ |url-status=live }}</ref> and the [[Nextstrain]] project has assigned it the clade identifiers 21K and 21L, both belonging to a larger Omicron group 21M.<ref name="CoVariants1">{{cite web |url=https://covariants.org/variants/21K.Omicron |title=Variant: 21K (Omicron) |author=<!--Not stated--> |date=28 November 2021 |website=covariants.org |publisher=CoVariants |access-date=28 November 2021 |quote=Variant 21K (Omicron) appears to have arisen in November 2021, possibly in South Africa. |archive-date=28 November 2021 |archive-url=https://web.archive.org/web/20211128215406/https://covariants.org/variants/21K.Omicron |url-status=live }}</ref>

== History ==
Omicron was first detected on 22 November 2021 in laboratories in [[Botswana]] and [[South Africa]] based on samples collected on 11–16 November,<ref name=":2b">{{cite journal | vauthors = Viana R, Moyo S, Amoako DG, Tegally H, Scheepers C, Althaus CL, Anyaneji UJ, Bester PA, Boni MF, Chand M, Choga WT, Colquhoun R, Davids M, Deforche K, Doolabh D, du Plessis L, Engelbrecht S, Everatt J, Giandhari J, Giovanetti M, Hardie D, Hill V, Hsiao NY, Iranzadeh A, Ismail A, Joseph C, Joseph R, Koopile L, Kosakovsky Pond SL, Kraemer MU, Kuate-Lere L, Laguda-Akingba O, Lesetedi-Mafoko O, Lessells RJ, Lockman S, Lucaci AG, Maharaj A, Mahlangu B, Maponga T, Mahlakwane K, Makatini Z, Marais G, Maruapula D, Masupu K, Matshaba M, Mayaphi S, Mbhele N, Mbulawa MB, Mendes A, Mlisana K, Mnguni A, Mohale T, Moir M, Moruisi K, Mosepele M, Motsatsi G, Motswaledi MS, Mphoyakgosi T, Msomi N, Mwangi PN, Naidoo Y, Ntuli N, Nyaga M, Olubayo L, Pillay S, Radibe B, Ramphal Y, Ramphal U, San JE, Scott L, Shapiro R, Singh L, Smith-Lawrence P, Stevens W, Strydom A, Subramoney K, Tebeila N, Tshiabuila D, Tsui J, van Wyk S, Weaver S, Wibmer CK, Wilkinson E, Wolter N, Zarebski AE, Zuze B, Goedhals D, Preiser W, Treurnicht F, Venter M, Williamson C, Pybus OG, Bhiman J, Glass A, Martin DP, Rambaut A, Gaseitsiwe S, von Gottberg A, de Oliveira T | title = Rapid epidemic expansion of the SARS-CoV-2 Omicron variant in southern Africa | journal = Nature | volume = 603 | issue = 7902 | pages = 679–686 | date = March 2022 | pmid = 35042229 | doi = 10.1038/s41586-022-04411-y | pmc = 8942855 | bibcode = 2022Natur.603..679V }}</ref> with the first known samples collected in [[Johannesburg]], [[South Africa]] on 8 November 2021.<ref>{{cite journal | vauthors = Dyer O | title = Covid-19: South Africa's surge in cases deepens alarm over omicron variant | journal = BMJ | volume = 375 | pages = n3013 | date = December 2021 | pmid = 34862184 | doi = 10.1136/bmj.n3013 | s2cid = 244842008 | doi-access = free | title-link = doi }}</ref> The first known cases outside of South Africa were two people who travelled on 11 November: one who flew from South Africa to [[Hong Kong]] via [[Qatar]], and another who travelled from [[Egypt]] to [[Belgium]] via [[Turkey]].<ref name=":3bb">{{cite journal | vauthors = Gu H, Krishnan P, Ng DY, Chang LD, Liu GY, Cheng SS, Hui MM, Fan MC, Wan JH, Lau LH, Cowling BJ, Peiris M, Poon LL | title = Probable Transmission of SARS-CoV-2 Omicron Variant in Quarantine Hotel, Hong Kong, China, November 2021 | journal = Emerging Infectious Diseases | volume = 28 | issue = 2 | pages = 460–462 | date = February 2022 | pmid = 34860154 | pmc = 8798678 | doi = 10.3201/eid2802.212422 }}</ref><ref name=":5">{{cite journal | vauthors = Planas D, Saunders N, Maes P, Guivel-Benhassine F, Planchais C, Buchrieser J, Bolland WH, Porrot F, Staropoli I, Lemoine F, Péré H, Veyer D, Puech J, Rodary J, Baele G, Dellicour S, Raymenants J, Gorissen S, Geenen C, Vanmechelen B, Wawina-Bokalanga T, Martí-Carreras J, Cuypers L, Sève A, Hocqueloux L, Prazuck T, Rey FA, Simon-Loriere E, Bruel T, Mouquet H, André E, Schwartz O | title = Considerable escape of SARS-CoV-2 Omicron to antibody neutralization | journal = Nature | volume = 602 | issue = 7898 | pages = 671–675 | date = February 2022 | pmid = 35016199 | doi = 10.1038/s41586-021-04389-z | bibcode = 2022Natur.602..671P | s2cid = 256823009 | doi-access = free | title-link = doi }}</ref> On 26 November 2021, the WHO designated B.1.1.529 as a [[variant of concern]] and named it "Omicron", after the [[Omicron|fifteenth letter in the Greek alphabet]].<ref name=":0b" /> By 6 January 2022, the variant had been confirmed in 149 countries.<ref name=":6">{{cite journal | vauthors = Saxena SK, Kumar S, Ansari S, Paweska JT, Maurya VK, Tripathi AK, Abdel-Moneim AS | title = Transmission dynamics and mutational prevalence of the novel Severe acute respiratory syndrome coronavirus-2 Omicron Variant of Concern | journal = Journal of Medical Virology | volume = 94 | issue = 5 | pages = 2160–2166 | date = May 2022 | pmid = 35050521 | pmc = 9015611 | doi = 10.1002/jmv.27611 }}</ref>

Retrospectively, Omicron cases have been detected as occurring earlier, in October 2021.<ref>https://assets.publishing.service.gov.uk/media/6214f9a4e90e0710acb254b8/Technical-Briefing-36-22.02.22.pdf</ref>

=== Origin hypotheses ===
Omicron did not evolve from any other variant, but instead diverged on a distinct track, perhaps in 2020.<ref name=":6" /><ref name="Wei2022" /> Competing hypotheses are being examined.

One origin hypothesis is that various mutations in the Omicron variant, comprising a 9-[[nucleotide]] sequence, may have been acquired from another coronavirus (known as [[HCoV-229E]]), responsible for the common cold.<ref name=":8">{{cite journal | vauthors = Alkhatib M, Salpini R, Carioti L, Ambrosio FA, D'Anna S, Duca L, Costa G, Bellocchi MC, Piermatteo L, Artese A, Santoro MM, Alcaro S, Svicher V, Ceccherini-Silberstein F | title = Update on SARS-CoV-2 Omicron Variant of Concern and Its Peculiar Mutational Profile | journal = Microbiology Spectrum | volume = 10 | issue = 2 | pages = e0273221 | date = April 2022 | pmid = 35352942 | doi = 10.1128/spectrum.02732-21 | pmc = 9045195 | veditors = Perez DR }}</ref> This is not entirely {{nowrap|unexpected{{hsp}}{{mdash}}}}{{hsp}}at times, viruses within the body acquire and swap segments of genetic material from each other, and this is one common means of mutation.<ref name=":8" />

A link with [[HIV]] infection may explain a large number of mutations in the sequence of the Omicron variant.<ref name=":7">{{cite journal | vauthors = Tarcsai KR, Corolciuc O, Tordai A, Ongrádi J | title = SARS-CoV-2 infection in HIV-infected patients: potential role in the high mutational load of the Omicron variant emerging in South Africa | journal = GeroScience | date = June 2022 | volume = 44 | issue = 5 | pages = 2337–2345 | pmid = 35739343 | pmc = 9225796 | doi = 10.1007/s11357-022-00603-6 }}</ref> Indeed, in order to be affected by such a high number of mutations, the virus must have been able to evolve a long time without killing its host, which can occur in people with a [[Immunodeficiency|weakened immune system]] who receive enough medical care to survive.<ref name=":7" /><ref>{{Cite news|date=1 December 2021|title=The mystery of where omicron came from — and why it matters|work=NPR|url=https://www.npr.org/sections/goatsandsoda/2021/12/01/1055803031/the-mystery-of-where-omicron-came-from-and-why-it-matters?t=1638988165590|access-date=8 December 2021|archive-date=9 December 2021|archive-url=https://web.archive.org/web/20211209102439/https://www.npr.org/sections/goatsandsoda/2021/12/01/1055803031/the-mystery-of-where-omicron-came-from-and-why-it-matters?t=1638988165590|url-status=live}}</ref> This is the case in HIV patients in South Africa, who represent about 14% of the population (as of 2017).<ref>{{cite journal | vauthors = Zungu N, Mabaso M, Ramlagan S, Simbayi L, Moyo S, Shisana O, Murangandi P, Igumbor E, Sigida S, Jooste S, Marinda E, Ayalew K, Zuma K | title = Is There Risk Compensation among HIV Infected Youth and Adults 15 Years and Older on Antiretroviral Treatment in South Africa? Findings from the 2017 National HIV Prevalence, Incidence, Behaviour and Communication Survey | journal = International Journal of Environmental Research and Public Health | volume = 19 | issue = 10 | page = 6156 | date = May 2022 | pmid = 35627693 | pmc = 9141949 | doi = 10.3390/ijerph19106156 | doi-access = free | title-link = doi }}</ref> HIV prevention could be key to reducing the risk of uncontrolled HIV driving the emergence of [[SARS-CoV-2]] variants.<ref name=":7" />

One hypothesis to explain the novel mutations is that [[SARS-CoV-2]] was transmitted from humans to mice and mutated in a population of [[Mouse|mice]] sometime between 2020 and 2021 before reinfecting humans.<ref name="Wei2022">{{cite journal | vauthors = Wei C, Shan KJ, Wang W, Zhang S, Huan Q, Qian W | title = Evidence for a mouse origin of the SARS-CoV-2 Omicron variant | journal = Journal of Genetics and Genomics = Yi Chuan Xue Bao | volume = 48 | issue = 12 | pages = 1111–1121 | date = December 2021 | pmid = 34954396 | pmc = 8702434 | doi = 10.1016/j.jgg.2021.12.003 }}</ref>

On 1 December 2022, a team of researchers from the [[Charité]] (Berlin) published a now-[[Retraction in academic publishing|retracted]] study in [[Science (journal)|Science]] that claimed that "data revealed genetically diverse Omicron ancestors already existed across Africa by August 2021".<ref>{{cite journal |title=RETRACTED: Gradual emergence followed by exponential spread of the SARS-CoV-2 Omicron variant in Africa |journal=Science |date = December 2022 |doi=10.1126/science.add8737 | vauthors = Fischer C, Maponga TG, Yadouleton A, Abílio N, Aboce E, Adewumi P, Afonso P, Akorli J, Andriamandimby SF, Anga L, Ashong Y, Beloufa MA, Bensalem A, Birtles R, Boumba AL, Bwanga F, Chaponda M, Chibukira P, Chico RM, Chileshe J, Chongwe G, Cissé A, D'Alessandro U, de Lamballerie XN, de Morais JF, Derrar F, Dia N, Diarra Y, Doumbia L, Drosten C, Dussart P, Echodu R, Eggers Y, Eloualid A, Faye O, Feldt T, Frühauf A, Halatoko A, Ilouga PV, Ismael N, Jambou R, Jarju S, Kamprad A, Katowa B, Kayiwa J, King'wara L, Koita O, Lacoste V, Lagare A, Landt O, Lekana-Douki SE, Lekana-Douki JB, Iipumbu E, Loemba H, Lutwama J, Mamadou S, Maman I, Manyisa B, Martinez PA, Matoba J, Mhuulu L, Moreira-Soto A, Mwangi J, N Dilimabaka N, Nassuna CA, Ndiath MO, Nepolo E, Njouom R, Nourlil J, Nyanjom SG, Odari EO, Okeng A, Ouoba JB, Owusu M, Owusu Donkor I, Phadu KK, Phillips RO, Preiser W, Ruhanya V, Salah F, Salifou S, Sall AA, Sylverken AA, Tagnouokam-Ngoupo PA, Tarnagda Z, Tchikaya FO, Tufa TB, Drexler JF |volume=378 |issue=6623 |pages=eadd8737 |pmid=36454863 |s2cid=254150265 |doi-access = free | title-link = doi }}{{Retracted|doi=10.1126/science.adg2821|pmid=36537892|https://retractionwatch.com/2022/12/20/contamination-leads-to-swift-retraction-for-science-paper-on-the-origins-of-omicron-in-africa/ ''Retraction Watch''|https://retractionwatch.com/retracted-coronavirus-covid-19-papers/ ''Retraction Watch''|intentional=yes}}</ref> After a re-analysis because of doubts,<ref>{{cite journal |title=Surprising Omicron origins study comes under scrutiny |date=6 December 2022 |journal=Nature |doi=10.1038/d41586-022-04357-1|first=Smriti|last=Mallapaty|volume=612 |issue=7940 |pages=387–388 |pmid=36474049 |bibcode=2022Natur.612..387M |s2cid=254402519 |doi-access = free | title-link = doi }}</ref> the team retracted the article on 20 December 2022, due to contamination of the samples.<ref>{{cite web |url=https://www.charite.de/en/service/press_reports/artikel/detail/study_on_the_origins_of_omicron_retracted/ |title=Study on the origins of Omicron retracted |date=20 December 2022 |access-date=24 December 2022 |website=www.charite.de |quote=In a subsequent analysis of residual samples, they were found to be contaminated. It is no longer possible to establish the source of the contamination. |archive-date=24 December 2022 |archive-url=https://web.archive.org/web/20221224075814/https://www.charite.de/en/service/press_reports/artikel/detail/study_on_the_origins_of_omicron_retracted/ |url-status=live }}</ref><ref>{{cite web |url=https://www.science.org/content/article/we-made-mistake-omicron-origin-study-retracted-after-widespread-criticism |title='We made a mistake.' Omicron origin study retracted after widespread criticism |website=science.org |date=20 December 2022 |access-date=24 December 2022 |quote=But [[Kristian G. Andersen|Kristian Andersen]] [...] says the gradual evolution theory was already "off the table" before the paper was published. |archive-date=24 December 2022 |archive-url=https://web.archive.org/web/20221224033738/https://www.science.org/content/article/we-made-mistake-omicron-origin-study-retracted-after-widespread-criticism |url-status=live }}</ref>

=== Spread ===
On 24 November 2021, the variant was first reported to the WHO from South Africa based on samples that had been collected from 14 to 16 November.<ref name=":2b" /> South African scientists were first alerted by samples from the very beginning of November where the PCR tests had S gene target failure (occurs in a few variants, but not in Delta which dominated in the country in October) and by a sudden increase of COVID-19 cases in Gauteng; sequencing revealed that more than 70 percent of samples collected in the province between 14 and 23 November were a new variant.<ref>{{cite news |date=29 November 2021 |title=Inside SA leg of Omicron variant discovery: A single test result, a missing gene, and an email |publisher=News24 |url=https://www.news24.com/news24/southafrica/investigations/covid19/inside-sa-leg-of-omicron-variant-discovery-a-single-test-result-a-missing-gene-and-an-email-20211128 |url-status=live |access-date=2 December 2021 |archive-url=https://web.archive.org/web/20211202095241/https://www.news24.com/news24/southafrica/investigations/covid19/inside-sa-leg-of-omicron-variant-discovery-a-single-test-result-a-missing-gene-and-an-email-20211128 |archive-date=2 December 2021 |vauthors=Cowan K}}</ref>

The first confirmed specimens of Omicron were collected on 8 November 2021, in South Africa and on 9 November, in Botswana.<ref name="nature-alert">{{cite journal |vauthors=Callaway E |date=December 2021 |title=Heavily mutated Omicron variant puts scientists on alert |url=https://www.nature.com/articles/d41586-021-03552-w |url-status=live |journal=Nature |volume=600 |issue=7887 |page=21 |bibcode=2021Natur.600...21C |doi=10.1038/d41586-021-03552-w |pmid=34824381 |archive-url=https://web.archive.org/web/20211126181902/https://www.nature.com/articles/d41586-021-03552-w |archive-date=26 November 2021 |access-date=26 November 2021 |s2cid=244660616}}</ref> Likely Omicron (SGTF) samples had occurred on 4 November 2021 in Pretoria, South Africa.{{citation needed|date=March 2023}}

When the WHO was alerted on 24 November, Hong Kong was the only place outside Africa that had confirmed a case of Omicron; one person who traveled from South Africa on 11 November, and another traveler who was cross-infected by this case while staying in the same quarantine hotel.<ref name=":3bb" />

On 25 November, one confirmed case was identified in [[Israel]] from a traveler returning from Malawi,<ref name="auto">{{Cite tweet|number=1464132888673280016|user=BNODesk|title=Statement from Israel's health ministry reporting 1 confirmed case of new coronavirus variant B.1.1.529|date=26 November 2021|access-date=26 November 2021}}</ref> along with two who returned from South Africa and one from Madagascar.<ref>{{cite news |date=26 November 2021 |title=מחוסנת ב-3 מנות ואישה שנסעה לאילת באוטובוס: המאומתים לזן החדשt |url=https://m.ynet.co.il/articles/syyt2za00y |url-status=live |archive-url=https://web.archive.org/web/20211127080101/https://m.ynet.co.il/articles/syyt2za00y |archive-date=27 November 2021 |access-date=28 November 2021 |newspaper=Ynet |language=Hebrew |quote="4 מאומתים לווריאנט החדש התגלו בארץ, רה"מ יקיים מסיבת עיתונאים ב-14:30" translated: "4 verified for the new variant were discovered in the country, the prime minister will hold a press conference at 14:30 |last1=ינקו |first1=אדיר |last2=שומפלבי |first2=אטילה }}</ref> All four initial cases reported from Botswana occurred among fully vaccinated individuals.<ref>{{cite web | last=Tlhankane | first=Spira | name-list-style=vanc | title=Four cases of the new COVID-19 variant recorded in Botswana | website=Mmegi Online | date=25 November 2021 | url=https://www.mmegi.bw/news/four-cases-of-the-new-covid-19-variant-recorded-in-botswana/news | archive-url=http://web.archive.org/web/20211126162027/https://www.mmegi.bw/news/four-cases-of-the-new-covid-19-variant-recorded-in-botswana/news | archive-date=26 November 2021 | url-status=live | access-date=4 September 2024}}</ref>

On 26 November, Belgium confirmed its first case; an unvaccinated person who had travelled from Egypt via Turkey on 11 November.<ref name=":5" /> All three initial confirmed and suspected cases reported from Israel occurred among fully vaccinated individuals,<ref name="auto" /> as did a single suspected case in Germany.<ref>{{cite news |date=27 November 2021 |title=Flughafen Frankfurt: Person mit Omikron-Verdacht war vollständig geimpft |language=de |trans-title=Frankfurt airport: Person suspected to be infected with Omicron Variant was fully vaccinated |work=Frankfurter Rundschau |url=https://www.fr.de/politik/corona-variante-omikron-mit-sehr-hoher-wahrscheinlichkeit-bereits-in-deutschland-zr-91143286.html |access-date=27 November 2021 |archive-url=https://web.archive.org/web/20211127155005/https://www.fr.de/politik/corona-variante-omikron-mit-sehr-hoher-wahrscheinlichkeit-bereits-in-deutschland-zr-91143286.html |archive-date=27 November 2021 |vauthors=Kesselgruber K}}</ref>

On 27 November, two cases were detected in the United Kingdom, another two in [[Munich]], Germany and one in [[Milan]], Italy.<ref name="first-cases-20211127">{{cite news |date=27 November 2021 |title=UK, Germany and Italy detect Omicron coronavirus variant cases |work=Reuters |url=https://www.reuters.com/world/concerns-over-covid-variant-trigger-more-travel-curbs-southern-africa-2021-11-27/ |url-status=live |access-date=27 November 2021 |archive-url=https://web.archive.org/web/20211127111521/https://www.reuters.com/world/concerns-over-covid-variant-trigger-more-travel-curbs-southern-africa-2021-11-27/ |archive-date=27 November 2021}}</ref>

On 28 November 13 cases were confirmed in the Netherlands among the 624 airline passengers who arrived from South Africa on 26 November.<ref>{{Cite web |title=Coronavirus variant Omicron found in 13 positive tests so far {{!}} RIVM |url=https://www.rivm.nl/en/news/coronavirus-variant-omicron-found-in-13-positive-tests-so-far |url-status=live |archive-url=https://web.archive.org/web/20211206034210/https://www.rivm.nl/en/news/coronavirus-variant-omicron-found-in-13-positive-tests-so-far |archive-date=6 December 2021 |access-date=6 December 2021 |website=www.rivm.nl}}</ref> Confirmation of a further 5 cases among these passengers followed later.<ref name="rivm-actueel">{{Cite web |date=4 December 2021 |title=Actuele informatie over COVID-19 {{!}} RIVM |trans-title=Current information about COVID-19 {{!}} RIVM |url=https://www.rivm.nl/coronavirus-covid-19/actueel |url-status=live |archive-url=https://web.archive.org/web/20200406034057/https://www.rivm.nl/actuele-informatie-over-coronavirus |archive-date=6 April 2020 |access-date=6 December 2021 |website=www.rivm.nl |language=nl}}</ref> Entry into the Netherlands generally required having been vaccinated or PCR-tested, or having recovered. The passengers of these two flights had been tested upon arrival because of the newly imposed restrictions (which were set in place during their flight), after which 61 tested positive for SARS-CoV-2.<ref>{{cite news |date=27 November 2021 |title=61 travellers from South Africa in Netherlands positive for COVID-19 – authorities |work=Reuters |location=Amsterdam |url=https://www.reuters.com/world/europe/passengers-south-africa-face-wait-covid-19-testing-amsterdam-2021-11-26/ |url-status=live |access-date=27 November 2021 |archive-url=https://web.archive.org/web/20211126234507/https://www.reuters.com/world/europe/passengers-south-africa-face-wait-covid-19-testing-amsterdam-2021-11-26/ |archive-date=26 November 2021}}</ref> A further two cases were detected in Australia. Both people landed in [[Sydney]] the previous day, and travelled from southern Africa to [[Sydney Airport]] via [[Doha Airport]]. The two people, who were fully vaccinated, entered isolation; 12 other travellers from southern Africa also entered quarantine for fourteen days, while about 260 other passengers and crew on the flight were directed to isolate.<ref name="NSW-28Nov">{{cite news |date=28 November 2021 |title=Travellers test positive to Omicron COVID-19 strain after arriving in Sydney from southern Africa, NSW Health says |website=ABC News |url=https://www.abc.net.au/news/2021-11-28/tavellers-test-positive-omicron-covid-sydney/100657076 |url-status=live |access-date=28 November 2021 |archive-url=https://web.archive.org/web/20211128065804/https://www.abc.net.au/news/2021-11-28/tavellers-test-positive-omicron-covid-sydney/100657076 |archive-date=28 November 2021}}</ref> Two travellers from South Africa who landed in Denmark tested positive for COVID-19; it was confirmed on 28 November that both carried the Omicron variant.<ref>{{Cite news |date=28 November 2021 |title=To personer er indrejst i Danmark med coronavarianten Omikron |language=da |trans-title=Two people have entered Denmark with the corona variant Omicron |website=www.bt.dk |url=https://www.bt.dk/content/item/1555550 |url-status=live |access-date=28 November 2021 |archive-url=https://web.archive.org/web/20211128215258/https://www.bt.dk/samfund/ssi-to-i-danmark-er-bekraeftet-smittet-med-ny-coronavariant-0 |archive-date=28 November 2021}}</ref><ref>{{Cite news | vauthors = Ritzau A |date=28 November 2021 |title=Nu er det bekræftet: To personer smittet med Omikron rejst ind i Danmark |language=da |trans-title=Now it has been confirmed: Two people infected with Omicron traveled into Denmark |website=ekstrabladet.dk |url=https://ekstrabladet.dk/nyheder/samfund/nu-er-det-bekraeftet-to-personer-smittet-med-omikron-rejst-ind-i-danmark/9014646 |url-status=live |access-date=28 November 2021 |archive-url=https://web.archive.org/web/20211128215232/https://ekstrabladet.dk/nyheder/samfund/nu-er-det-bekraeftet-to-personer-smittet-med-omikron-rejst-ind-i-danmark/9014646 |archive-date=28 November 2021}}</ref> On the same day, Austria also confirmed its first Omicron case.<ref>{{Cite web |title=Austria detects suspect Omicron case as Europe battles virus surge |url=https://www.wionews.com/world/austria-detects-suspect-omicron-case-as-europe-battles-virus-surge-432567 |url-status=live |archive-url=https://web.archive.org/web/20211128215259/https://www.wionews.com/world/austria-detects-suspect-omicron-case-as-europe-battles-virus-surge-432567 |archive-date=28 November 2021 |access-date=28 November 2021 |website=WION|date=28 November 2021 }}</ref> A detected Omicron case was reported in the Czech Republic, from a traveler who spent time in Namibia.<ref name="auto3">{{cite news |date=28 November 2021 |title=Omicron variant found in UK, Germany, Czech Republic |website=New York Post |url=https://nypost.com/2021/11/27/omicron-variant-found-in-uk-germany-czech-republic/ |url-status=live |access-date=28 November 2021 |archive-url=https://web.archive.org/web/20211127230155/https://nypost.com/2021/11/27/omicron-variant-found-in-uk-germany-czech-republic/ |archive-date=27 November 2021}}</ref> Canada also reported its first Omicron cases, with two from travelers from Nigeria, therefore becoming the first North American country to report an Omicron case.<ref name="auto1">{{Cite news |date=28 November 2021 |title=Canada, Netherland, Australia latest countries reporting cases of omicron COVID-19 variant |website=ABC13 |url=https://abc13.com/omicron-variant-new-covid-netherlands-coronavirus/11276819/ |url-status=live |access-date=28 November 2021 |archive-url=https://web.archive.org/web/20211128140018/https://abc13.com/omicron-variant-new-covid-netherlands-coronavirus/11276819/ |archive-date=28 November 2021}}</ref>

On 29 November, a positive case was recorded in [[Darwin, Northern Territory|Darwin]], Australia. The person arrived in Darwin on a repatriation flight from Johannesburg, South Africa on 25 November, and was taken to a quarantine facility, where the positive test was recorded.<ref>{{cite news |date=29 November 2021 |title=COVID-positive repatriation flight arrival to the Northern Territory tests positive to Omicron variant |website=ABC News |url=https://www.abc.net.au/news/2021-11-29/nt-covid-outbreak-katherine-traveller-positive-for-omicron/100657690 |url-status=live |access-date=29 November 2021 |archive-url=https://web.archive.org/web/20211129013820/https://www.abc.net.au/news/2021-11-29/nt-covid-outbreak-katherine-traveller-positive-for-omicron/100657690 |archive-date=29 November 2021 |vauthors=Perera A}}</ref> Two more people who travelled to Sydney from southern Africa via Singapore tested positive.<ref name="Aus29Nov">{{cite news |date=29 November 2021 |title=NSW Health confirms two more Omicron COVID-19 cases in travellers from southern Africa |website=ABC News |url=https://www.abc.net.au/news/2021-11-29/nsw-health-confirms-two-more-omicron-covid-cases-in-sydney/100658728 |url-status=live |access-date=29 November 2021 |archive-url=https://web.archive.org/web/20211129115753/https://www.abc.net.au/news/2021-11-29/nsw-health-confirms-two-more-omicron-covid-cases-in-sydney/100658728 |archive-date=29 November 2021 |vauthors=Nguyen K}}</ref> Portugal reported 13 Omicron cases, all of them members of a soccer club.<ref>{{cite news |date=29 November 2021 |title=Live updates: Omicron variant |work=Cable News Network |url=https://www.cnn.com/world/live-news/covid-variant-omicron-11-29-21/index.html |url-status=live |access-date=29 November 2021 |archive-url=https://web.archive.org/web/20211130120226/https://www.cnn.com/world/live-news/covid-variant-omicron-11-29-21/index.html |archive-date=30 November 2021}}</ref> Sweden also confirmed their first case on 29 November,<ref name=":3b">{{Cite news |date=29 November 2021 |title=Första fallet av omikron upptäckt i Sverige |language=sv |trans-title=The first case of omicron detection in Sweden |website=www.aftonbladet.se |url=https://www.aftonbladet.se/a/Poazg6 |url-status=live |access-date=29 November 2021 |archive-url=https://web.archive.org/web/20211130210048/https://www.aftonbladet.se/a/Poazg6 |archive-date=30 November 2021}}</ref> as did Spain, when a traveler came from South Africa.<ref>{{Cite news |date=29 November 2021 |title=Spain detects first Omicron case, COVID-19 infections rise |work=Reuters |url=https://www.reuters.com/world/europe/spain-detects-first-omicron-case-covid-19-2021-11-29/ |url-status=live |access-date=30 November 2021 |archive-url=https://web.archive.org/web/20211130205826/https://www.reuters.com/world/europe/spain-detects-first-omicron-case-covid-19-2021-11-29/ |archive-date=30 November 2021}}</ref>

On 30 November, the Netherlands reported that Omicron cases had been detected in two samples dating back as early as 19 November.<ref name="auto6">{{Cite web |title=Omicron variant found in two previous test samples {{!}} RIVM |url=https://www.rivm.nl/en/news/omicron-variant-found-in-two-previous-test-samples |url-status=live |archive-url=https://web.archive.org/web/20211204013520/https://www.rivm.nl/en/news/omicron-variant-found-in-two-previous-test-samples |archive-date=4 December 2021 |access-date=6 December 2021 |website=www.rivm.nl}}</ref> A positive case was recorded in Sydney from a traveller who had visited southern Africa before travel restrictions were imposed, and was subsequently active in the community.<ref name="NSW30Nov">{{cite news |date=30 November 2021 |title=NSW records fifth case of Omicron COVID-19 variant as two more potential infections investigated |website=ABC News |url=https://www.abc.net.au/news/2021-11-30/nsw-covid-19-omicron-update-new-case-discovered/100661108 |url-status=live |access-date=30 November 2021 |archive-url=https://web.archive.org/web/20211130040038/https://www.abc.net.au/news/2021-11-30/nsw-covid-19-omicron-update-new-case-discovered/100661108 |archive-date=30 November 2021}}</ref> Japan also confirmed its first case.<ref>{{cite news |date=30 November 2021 |title=Japan's first Omicron case may help portray PM Kishida as decisive |website=Reuters |url=https://www.reuters.com/business/healthcare-pharmaceuticals/japan-confirms-first-case-omicron-variant-coronavirus-kyodo-2021-11-30/ |url-status=live |access-date=30 November 2021 |archive-url=https://web.archive.org/web/20211130205827/https://www.reuters.com/business/healthcare-pharmaceuticals/japan-confirms-first-case-omicron-variant-coronavirus-kyodo-2021-11-30/ |archive-date=30 November 2021}}</ref> Two Israeli doctors tested positive and entered isolation. Both of them had received three shots of the Pfizer vaccine prior to testing positive.<ref name="jpost.com">{{Cite web |title=Two Israeli doctors test positive for Omicron COVID variant |url=https://www.jpost.com/health-and-wellness/coronavirus/two-israeli-doctors-test-positive-for-omicron-covid-variant-687412 |url-status=live |archive-url=https://web.archive.org/web/20211231015948/https://www.jpost.com/health-and-wellness/coronavirus/two-israeli-doctors-test-positive-for-omicron-covid-variant-687412 |archive-date=31 December 2021 |access-date=30 November 2021 |website=The Jerusalem Post |date=30 November 2021 }}</ref> In Brazil, three cases of the Omicron variant were confirmed in [[São Paulo (state)|São Paulo]].<ref>{{cite web |date=1 December 2021 |title=SP confirma terceiro caso da variante ômicron |trans-title=SP confirms third case of ômicron variant |url=https://g1.globo.com/google/amp/sp/sao-paulo/noticia/2021/12/01/sp-confirma-terceiro-caso-da-variante-omicron-no-brasil.ghtml |url-status=live |archive-url=https://web.archive.org/web/20211201145527/https://g1.globo.com/google/amp/sp/sao-paulo/noticia/2021/12/01/sp-confirma-terceiro-caso-da-variante-omicron-no-brasil.ghtml |archive-date=1 December 2021 |access-date=1 December 2021 |website=g1 |language=pt-br}}</ref> Another five are under suspicion.<ref>{{Cite web |date=30 November 2021 |title=O que se sabe sobre os primeiros casos confirmados da variante Ômicron no Brasil |trans-title=What is known about the first confirmed cases of the Ômicron variant in Brazil |url=https://www.cnnbrasil.com.br/saude/o-que-se-sabe-sobre-os-primeiros-casos-confirmados-da-variante-omicron-no-brasil/ |url-status=live |archive-url=https://web.archive.org/web/20211201021617/https://www.cnnbrasil.com.br/saude/o-que-se-sabe-sobre-os-primeiros-casos-confirmados-da-variante-omicron-no-brasil/ |archive-date=1 December 2021 |access-date=1 December 2021 |website=CNN Brasil |language=pt-br}}</ref><ref>{{Cite web |date=30 November 2021 |title=Passa para 6 o número de casos suspeitos da variante Ômicron investigados no Brasil |trans-title=The number of suspected cases of the Ômicron variant investigated in Brazil goes to 6 |url=https://www.cnnbrasil.com.br/saude/passa-para-6-o-numero-de-casos-suspeitos-da-variante-omicron-investigados-no-brasil/ |url-status=live |archive-url=https://web.archive.org/web/20211201022247/https://www.cnnbrasil.com.br/saude/passa-para-6-o-numero-de-casos-suspeitos-da-variante-omicron-investigados-no-brasil/ |archive-date=1 December 2021 |access-date=1 December 2021 |work=CNN Brasil |language=pt-br}}</ref> A person in [[Leipzig]], Germany with no travel history nor contact with travellers tested positive for Omicron.<ref>{{Cite web |title=Germany: Leipzig reports first Omicron variant case with no travel history |url=https://www.freepressjournal.in/world/germany-leipzig-reports-first-omicron-variant-case-with-no-travel-history |url-status=live |archive-url=https://web.archive.org/web/20211201222511/https://www.freepressjournal.in/world/germany-leipzig-reports-first-omicron-variant-case-with-no-travel-history |archive-date=1 December 2021 |access-date=1 December 2021 |website=Free Press Journal}}</ref>

On 1 December, the Omicron variant was detected in three samples in Nigeria that had been collected from travelers from South Africa within the last week.<ref name="NYT-20211201">{{cite news |date=1 December 2021 |title=Ghana and Nigeria are the latest African countries to detect the Omicron variant |work=[[The New York Times]] |url=https://www.nytimes.com/2021/12/01/world/africa/nigeria-omicron.html |url-status=live |access-date=2 December 2021 |archive-url=https://web.archive.org/web/20211202002235/https://www.nytimes.com/2021/12/01/world/africa/nigeria-omicron.html |archive-date=2 December 2021 |vauthors=Dahir A, Ezeamalu B, Pérez-Peña R}}</ref><ref name="Reuters Nigeria 1Dec">{{cite news |date=1 December 2021 |title=Nigeria confirms first cases of Omicron among travellers from South Africa |publisher=Reuters |url=https://www.reuters.com/world/africa/nigeria-confirms-first-cases-omicron-among-travellers-south-africa-2021-12-01/ |url-status=live |access-date=1 December 2021 |archive-url=https://web.archive.org/web/20211201073701/https://www.reuters.com/world/africa/nigeria-confirms-first-cases-omicron-among-travellers-south-africa-2021-12-01/ |archive-date=1 December 2021}}</ref> On the same day, public health authorities in the United States announced the country's first confirmed Omicron case. A resident of [[San Francisco]] who had been vaccinated returned from South Africa on 22 November, began showing mild symptoms on 25 November<ref>{{cite news |date=1 December 2021 |title=First case of omicron in US identified in San Francisco |work=[[San Francisco Chronicle]] |url=https://www.sfgate.com/bayarea/article/omicron-San-Francisco-first-case-in-US-COVID-16666494.php |url-status=live |access-date=1 December 2021 |archive-url=https://web.archive.org/web/20211201195321/https://www.sfgate.com/bayarea/article/omicron-San-Francisco-first-case-in-US-COVID-16666494.php |archive-date=1 December 2021 |vauthors=Graff A}}</ref> and was confirmed to have a mild case of COVID-19 on 29 November.<ref>{{cite news |date=1 December 2021 |title=First U.S. Case of Omicron Variant Found in San Francisco Resident |publisher=[[KQED Inc.|KQED]] |location=San Francisco |url=https://www.kqed.org/science/1977807/first-u-s-case-of-omicron-variant-found-in-california |url-status=live |access-date=1 December 2021 |archive-url=https://web.archive.org/web/20211201235257/https://www.kqed.org/science/1977807/first-u-s-case-of-omicron-variant-found-in-california |archive-date=1 December 2021 |vauthors=Stark K, Rodriguez JF, Dillon RM}}</ref> Ireland and South Korea also reported their first cases.<ref>{{cite news |date=1 December 2021 |title=Case of Omicron variant confirmed in Ireland |publisher=[[RTÉ News and Current Affairs]] |url=https://www.rte.ie/news/coronavirus/2021/1201/1264223-ireland-nphet/ |url-status=live |access-date=12 December 2021 |archive-url=https://web.archive.org/web/20211203225106/https://www.rte.ie/news/coronavirus/2021/1201/1264223-ireland-nphet/ |archive-date=3 December 2021 |vauthors=O'Donnell D}}</ref> South Korea reported its cases from five travelers arriving in South Korea from Nigeria.<ref>{{cite news |date=1 December 2021 |title=South Korea reports five Omicron cases on flight from Nigeria |work=Reuters |url=https://www.reuters.com/business/healthcare-pharmaceuticals/south-korea-reports-daily-record-over-5000-new-covid-19-infections-2021-12-01/ |url-status=live |access-date=1 December 2021 |archive-url=https://web.archive.org/web/20211201040044/https://www.reuters.com/business/healthcare-pharmaceuticals/south-korea-reports-daily-record-over-5000-new-covid-19-infections-2021-12-01/ |archive-date=1 December 2021}}</ref>

On 2 December, Dutch health authorities confirmed that all 14 passengers with confirmed Omicron infection on 26 November had been previously vaccinated.<ref>{{cite news |date=2 December 2021 |title=Dutch say 14 air passengers from S. Africa with Omicron were vaccinated |work=Reuters |url=https://www.reuters.com/world/europe/dutch-covid-19-quarantine-ends-most-safrica-passengers-authorities-2021-12-02/ |url-status=live |access-date=2 December 2021 |archive-url=https://web.archive.org/web/20211202090552/https://www.reuters.com/world/europe/dutch-covid-19-quarantine-ends-most-safrica-passengers-authorities-2021-12-02/ |archive-date=2 December 2021}}</ref> The same day, the [[Norwegian Institute of Public Health]] confirmed that 50 attendees of a company Christmas party held at a restaurant in Norway's capital, [[Oslo]], were infected with the Omicron variant.<ref name="Norway1">{{cite news |date=4 December 2021 |title=Number of confirmed omicron cases as of 3 December |work=[[Folkehelseinstituttet]] |url=https://www.fhi.no/nyheter/2021/antall-bekreftede-omikron-tilfeller-per-3.-desember/ |url-status=live |access-date=4 December 2021 |archive-url=https://web.archive.org/web/20211204085112/https://www.fhi.no/nyheter/2021/antall-bekreftede-omikron-tilfeller-per-3.-desember/ |archive-date=4 December 2021}}</ref> France has confirmed only 25 cases of the new Omicron variant but officials say the number could jump significantly in the coming weeks.<ref>{{Cite news |date=6 December 2021 |title=France now has 25 Omicron Covid variant cases – minister |work=[[Reuters]] |url=https://www.reuters.com/world/europe/france-now-has-25-omicron-covid-variant-cases-minister-2021-12-06/ |url-status=live |access-date=7 December 2021 |archive-url=https://web.archive.org/web/20211206232525/https://www.reuters.com/world/europe/france-now-has-25-omicron-covid-variant-cases-minister-2021-12-06/ |archive-date=6 December 2021}}</ref>

By 6 December, [[Malaysia]] confirmed its first case of the variant. The case was a South African student entering to study at a private university.<ref>{{Cite web |date=3 December 2021 |title=Omicron sudah sampai ke Malaysia |url=https://www.malaysiakini.com/news/601635 |url-status=live |archive-url=https://web.archive.org/web/20211203050931/https://www.malaysiakini.com/news/601635 |archive-date=3 December 2021 |access-date=8 December 2021 |website=Malaysiakini}}</ref> In Namibia, 18 cases out of 19 positive COVID-19 samples that had been collected between 11 and 26 November were found to be Omicron, indicating a high level of prevalence in the country.<ref>{{Cite news |date=6 December 2021 |title=Namibia detects Omicron coronavirus variant in 18 of 19 samples |work=Reuters |url=https://www.reuters.com/lifestyle/science/namibia-detects-omicron-coronavirus-variant-18-19-samples-2021-12-06/ |url-status=live |access-date=7 December 2021 |archive-url=https://web.archive.org/web/20211206230704/https://www.reuters.com/lifestyle/science/namibia-detects-omicron-coronavirus-variant-18-19-samples-2021-12-06/ |archive-date=6 December 2021}}</ref> Fiji also confirmed two positive cases of the variant. They travelled from Nigeria arriving in Fiji on 25 November.<ref>{{Cite web |date=7 December 2021 |title=Fijians test positive for Omicron variant – Govt |url=https://www.rnz.co.nz/international/pacific-news/457351/fijians-test-positive-for-omicron-variant-govt |url-status=live |archive-url=https://web.archive.org/web/20211206143715/https://www.rnz.co.nz/international/pacific-news/457351/fijians-test-positive-for-omicron-variant-govt |archive-date=6 December 2021 |access-date=8 December 2021 |website=RNZ }}</ref>

On 9 December, Richard Mihigo, coordinator of the World Health Organisation's Immunisation and Vaccine Development Programme for Africa, announced that Africa accounted for 46% of reported cases of the Omicron variant globally.<ref>{{Cite news |date=9 December 2021 |title=Africa accounts for 46% of reported cases of Omicron, WHO official says |work=Reuters |url=https://www.reuters.com/world/africa/africa-accounts-36-reported-cases-omicron-who-official-says-2021-12-09/ |url-status=live |access-date=9 December 2021 |archive-url=https://web.archive.org/web/20211210094245/https://www.reuters.com/world/africa/africa-accounts-36-reported-cases-omicron-who-official-says-2021-12-09/ |archive-date=10 December 2021}}</ref>

On 13 December, the first death of a person with Omicron was reported in the UK.<ref>{{Cite news |date=13 December 2021 |title=Covid: First UK death recorded with Omicron variant |work=BBC News |url=https://www.bbc.com/news/uk-59639007 |url-status=live |access-date=13 December 2021 |archive-url=https://web.archive.org/web/20211220204740/https://www.bbc.com/news/uk-59639007 |archive-date=20 December 2021}}</ref>

On 16 December, New Zealand confirmed its first case of the Omicron variant, an individual who had traveled from Germany via Dubai.<ref>{{cite web |date=16 December 2021 |title=First Omicron case detected in New Zealand |url=https://www.health.govt.nz/news-media/media-releases/first-omicron-case-detected-new-zealand |url-status=live |archive-url=https://web.archive.org/web/20211220233733/https://www.health.govt.nz/news-media/media-releases/first-omicron-case-detected-new-zealand |archive-date=20 December 2021 |access-date=16 December 2021 |publisher=[[Ministry of Health (New Zealand)|Ministry of Healfh]]}}</ref>

The first death of a person with Omicron was reported in Germany on 23 December<ref name="DW1">{{cite news |date=23 December 2021 |title=COVID: Germany records first death from omicron variant |work=DW |url=https://www.dw.com/en/covid-germany-records-first-death-from-omicron-variant/a-60241594 |url-status=live |access-date=23 December 2021 |archive-url=https://web.archive.org/web/20211224001839/https://www.dw.com/en/covid-germany-records-first-death-from-omicron-variant/a-60241594 |archive-date=24 December 2021}}</ref> and in Australia on 27 December.<ref>{{cite news |date=27 December 2021 |title=Australia: Omicron death, false negative COVID results |work=Al Jazeera |url=https://www.aljazeera.com/news/2021/12/27/australia-records-first-omicron-death-in-new-south-wales |url-status=live |access-date=27 December 2021 |archive-url=https://web.archive.org/web/20211227224035/https://www.aljazeera.com/news/2021/12/27/australia-records-first-omicron-death-in-new-south-wales |archive-date=27 December 2021}}</ref>

By Christmas 2021, the Omicron Strain became dominant in the US.<ref>{{Cite news |date=28 December 2021 |title=U.S. CDC estimates Omicron variant to be 58.6% of cases, revises projection |work=Reuters |url=https://www.reuters.com/world/us/omicron-estimated-be-586-coronavirus-variants-us-cdc-2021-12-28/ |access-date=15 April 2022 |archive-date=6 March 2022 |archive-url=https://web.archive.org/web/20220306205528/https://www.reuters.com/world/us/omicron-estimated-be-586-coronavirus-variants-us-cdc-2021-12-28/ |url-status=live }}</ref>

On 3 January 2022, South Korea reported the first two deaths of people who tested positive [[post mortem]] for Omicron.<ref>{{Cite news |date=3 January 2022 |title=S.Korea reports first deaths linked to Omicron coronavirus variant – Yonhap |work=Reuters |url=https://www.reuters.com/business/healthcare-pharmaceuticals/skorea-reports-first-deaths-linked-omicron-coronavirus-variant-yonhap-2022-01-03/ |url-status=live |access-date=3 January 2022 |archive-url=https://web.archive.org/web/20220103220903/https://www.reuters.com/business/healthcare-pharmaceuticals/skorea-reports-first-deaths-linked-omicron-coronavirus-variant-yonhap-2022-01-03/ |archive-date=3 January 2022}}</ref>

In February 2022, Omicron accounted for 98% of publicly available genetic sequences worldwide.<ref name="who-definitions-2023"/>

On 29 March 2022, Omicron subvariant BA.2 overtook BA.1 and became the dominant strain in the US.<ref>{{Cite web |last=Goodman |first=Brenda |name-list-style=vanc |title=Omicron subvariant BA.2 is now the dominant strain of Covid-19 in the US, CDC says |url=https://www.cnn.com/2022/03/29/health/ba-2-dominant-us/index.html |access-date=29 March 2022 |website=CNN |date=29 March 2022 |archive-date=29 March 2022 |archive-url=https://web.archive.org/web/20220329143717/https://www.cnn.com/2022/03/29/health/ba-2-dominant-us/index.html |url-status=live }}</ref><ref>{{Cite web |last=McDade |first=Aaron |name-list-style=vanc |date=29 March 2022 |title=Omicron BA.2 sub-variant now dominant in U.S., CDC says |url=https://www.newsweek.com/ba-2-covid-sub-variant-dominant-stealth-variant-1692964 |access-date=29 March 2022 |website=Newsweek }}</ref><ref>{{Cite web |last=CDC |date=28 March 2020 |title=COVID Data Tracker |url=https://covid.cdc.gov/covid-data-tracker |access-date=29 March 2022 |website=Centers for Disease Control and Prevention |archive-date=22 May 2021 |archive-url=https://web.archive.org/web/20210522045354/https://covid.cdc.gov/covid-data-tracker/ |url-status=live }}</ref>

As of May 2022, BA.2.12.1 was spreading in the US and two new subvariants of Omicron named BA.4 and BA.5, first detected in January 2022, spread in South Africa. All 3 subvariants have spike protein mutations of L452 and elude immunity from prior BA1 infection.<ref name="science52022">{{Cite journal |last=Gretchen Vogel |date=22 May 2022 |title=New versions of Omicron are masters of immune evasion |url=https://www.science.org/content/article/new-versions-omicron-are-masters-immune-evasion |journal=Science |access-date=20 November 2022 |archive-date=7 March 2023 |archive-url=https://web.archive.org/web/20230307032219/https://www.science.org/content/article/new-versions-omicron-are-masters-immune-evasion |url-status=live }}</ref>

On 16 March 2023, without seeing a reduction in the threat to public health, the WHO stopped classifying Omicron as a variant of concern in order to maintain this classification only for new threats. Instead, the WHO classified its subvariants as variants of interest and under monitoring.<ref name="who-definitions-2023">{{cite press release |type=Statement |date=16 March 2023 |title=Statement on the update of WHO's working definitions and tracking system for SARS-CoV-2 variants of concern and variants of interest |url=https://www.who.int/news/item/16-03-2023-statement-on-the-update-of-who-s-working-definitions-and-tracking-system-for-sars-cov-2-variants-of-concern-and-variants-of-interest |publisher=World Health Organization |access-date=20 May 2023 |archive-date=8 June 2023 |archive-url=https://web.archive.org/web/20230608191442/https://www.who.int/news/item/16-03-2023-statement-on-the-update-of-who-s-working-definitions-and-tracking-system-for-sars-cov-2-variants-of-concern-and-variants-of-interest |url-status=live }}</ref>

== Reactions ==

=== Vaccine producers ===
On 26 November 2021, [[BioNTech]] said it would know in two weeks whether the current vaccine is effective against the variant and that an updated vaccine could be shipped in 100 days if necessary. [[AstraZeneca]], [[Moderna]] and [[Johnson & Johnson]] were also studying the variant's impact on the effectiveness of their vaccines.<ref>{{cite news |date=26 November 2021 |title=BioNTech says it could tweak Covid vaccine in 100 days if needed |work=The Guardian |url=https://www.theguardian.com/society/2021/nov/26/biontech-says-it-could-tweak-covid-vaccine-in-100-days-if-needed |url-status=live |access-date=27 November 2021 |archive-url=https://web.archive.org/web/20211127000415/https://www.theguardian.com/society/2021/nov/26/biontech-says-it-could-tweak-covid-vaccine-in-100-days-if-needed |archive-date=27 November 2021}}</ref> On the same day, [[Novavax]] stated that it was developing an updated vaccine requiring two doses for the Omicron variant, which the company expected to be ready for testing and manufacturing within a few weeks.<ref>{{cite news |date=30 November 2021 |title=Novavax developing vaccine that targets new COVID-19 variant |work=CBS Baltimore Staff |url=https://www.reuters.com/business/healthcare-pharmaceuticals/novavax-testing-vaccine-that-targets-new-covid-19-variant-2021-11-26/ |url-status=live |access-date=4 December 2021 |archive-url=https://web.archive.org/web/20211202201620/https://baltimore.cbslocal.com/2021/11/30/maryland-based-vaccine-manufacturer-developing-covid-19-vaccine-targeting-omicron-variant/ |archive-date=2 December 2021}}</ref><ref>{{cite news |date=26 November 2021 |title=Maryland-Based Vaccine Manufacturer Developing COVID-19 Vaccine That Targets Omicron Variant |agency=Reuters |url=https://baltimore.cbslocal.com/2021/11/30/maryland-based-vaccine-manufacturer-developing-covid-19-vaccine-targeting-omicron-variant/ |url-status=live |access-date=30 November 2021 |archive-url=https://web.archive.org/web/20211128204342/https://www.reuters.com/business/healthcare-pharmaceuticals/novavax-testing-vaccine-that-targets-new-covid-19-variant-2021-11-26/ |archive-date=28 November 2021 |vauthors=Maddipatla M, Roy M}}</ref> On 29 November 2021, The [[Gamaleya Institute]] said that [[Sputnik Light]] should be effective against the variant, that it would begin adapting [[Sputnik V COVID-19 vaccine|Sputnik V]], and that a modified version could be ready for mass production in 45 days.<ref>{{cite news |date=29 November 2021 |title=Sputnik V maker: Vaccine could be adapted to fight omicron |work=ABC News |agency=Associated Press |location=Moscow |url=https://abcnews.go.com/Health/wireStory/sputnik-maker-vaccine-adapted-fight-omicron-81447527 |url-status=live |access-date=29 November 2021 |archive-url=https://web.archive.org/web/20211202045016/https://abcnews.go.com/Health/wireStory/sputnik-maker-vaccine-adapted-fight-omicron-81447527 |archive-date=2 December 2021}}</ref> [[Sinovac]] said it could quickly mass-produce an inactivated vaccine against the variant and that it was monitoring studies and collecting samples of the variant to determine if a new vaccine is needed.<ref>{{Cite web |date=29 November 2021 |title=Sinovac and world's Covid-19 vaccine makers 'ready' to produce Omicron jab |url=https://www.scmp.com/news/china/science/article/3157730/chinas-sinovac-ready-produce-targeted-omicron-vaccine-if |url-status=live |archive-url=https://web.archive.org/web/20211130210011/https://www.scmp.com/news/china/science/article/3157730/chinas-sinovac-ready-produce-targeted-omicron-vaccine-if |archive-date=30 November 2021 |access-date=29 November 2021 |website=South China Morning Post}}</ref>

On 7 December 2021, at a symposium in Brazil with its partner [[Instituto Butantan]], Sinovac said it would update its vaccine to the new variant and make it available in three months.<ref>{{cite news |date=7 December 2021 |title=Sinovac prevê atualização da Coronavac para variante Ômicron em até três meses |language=Portuguese |trans-title=Sinovac plans to update Coronavac to the Omicron variant within three months |work=CNN Brazil |url=https://www.cnnbrasil.com.br/saude/butantan-preve-atualizacao-da-coronavac-para-variante-omicron-em-ate-tres-meses/ |url-status=live |access-date=9 December 2021 |archive-url=https://web.archive.org/web/20211209104555/https://www.cnnbrasil.com.br/saude/butantan-preve-atualizacao-da-coronavac-para-variante-omicron-em-ate-tres-meses/ |archive-date=9 December 2021}}</ref> On 2 December, the [[Finlay Institute]] was already developing a version of [[Soberana Plus]] against the variant.<ref>{{cite news |date=2 December 2021 |title=Cuba to update domestic vaccine to battle Omicron |work=Al Jazeera |url=https://www.aljazeera.com/news/2021/12/2/cuba-to-update-domestic-vaccine-to-battle-omicron |url-status=live |access-date=20 December 2021 |archive-url=https://web.archive.org/web/20211220194822/https://www.aljazeera.com/news/2021/12/2/cuba-to-update-domestic-vaccine-to-battle-omicron |archive-date=20 December 2021}}</ref> Pfizer hoped to have a vaccine targeted to immunize against Omicron ready by March 2022.<ref>{{Cite web |date=10 January 2022 |title=Pfizer CEO says omicron vaccine will be ready in March |url=https://www.cnbc.com/2022/01/10/covid-vaccine-pfizer-ceo-says-omicron-vaccine-will-be-ready-in-march.html |url-status=live |archive-url=https://web.archive.org/web/20220126210708/https://www.cnbc.com/2022/01/10/covid-vaccine-pfizer-ceo-says-omicron-vaccine-will-be-ready-in-march.html |archive-date=26 January 2022 |access-date=27 January 2022 |website=CNBC |vauthors=Spencer K}}</ref>

=== World Health Organization ===

On 26 November 2021, the WHO asked nations to enhance surveillance and sequencing efforts, submit complete genome sequences and associated metadata to a publicly available database, such as [[GISAID]], report initial cases/clusters associated with virus-of-concern infection to the WHO through the [[International Health Regulations]] (IHR) mechanism, where capacity exists and in coordination with the international community, perform field investigations and laboratory assessments to improve understanding of the potential impacts of the virus of concern on COVID-19 epidemiology, severity, and the effectiveness of public health and social measures, diagnostic methods, immune responses, antibody neutralization, or other relevant characteristics.<ref>{{Cite web |date=26 November 2021 |title=Classification of Omicron (B.1.1.529): SARS-CoV-2 Variant of Concern |url=https://www.who.int/news/item/26-11-2021-classification-of-omicron-(b.1.1.529)-sars-cov-2-variant-of-concern |url-status=live |archive-url=https://web.archive.org/web/20211126181619/https://www.who.int/news/item/26-11-2021-classification-of-omicron-(b.1.1.529)-sars-cov-2-variant-of-concern |archive-date=26 November 2021 |website=[[World Health Organization]] (WHO)}}</ref>
On 26 November 2021, the WHO advised countries not to impose new restrictions on travel, instead recommending a "risk-based and scientific" approach to travel measures.<ref>{{cite news |date=26 November 2021 |title=WHO cautions against imposing travel restrictions due to new variant |work=[[Reuters]] |location=Geneva |url=https://www.reuters.com/world/who-cautions-against-imposing-travel-restrictions-due-new-variant-2021-11-26/ |url-status=live |access-date=26 November 2021 |archive-url=https://web.archive.org/web/20211126113434/https://www.reuters.com/world/who-cautions-against-imposing-travel-restrictions-due-new-variant-2021-11-26/ |archive-date=26 November 2021}}</ref> On the same day, the [[European Centre for Disease Prevention and Control]] (ECDC) reported modeling indicating that strict travel restrictions would delay the variant's impact on European countries by two weeks, possibly allowing countries to prepare for it.<ref name="ecdc-threat-assessment-brief">{{cite web |title=Implications of the emergence and spread of the SARS-CoV-2 B.1.1.529 variant of concern (Omicron) for the EU/EEA |url=https://www.ecdc.europa.eu/sites/default/files/documents/Implications-emergence-spread-SARS-CoV-2%20B.1.1.529-variant-concern-Omicron-for-the-EU-EEA-Nov2021.pdf |website=ecdc.europa.eu |access-date=26 November 2021 |archive-date=26 November 2021 |archive-url=https://web.archive.org/web/20211126212442/https://www.ecdc.europa.eu/sites/default/files/documents/Implications-emergence-spread-SARS-CoV-2%20B.1.1.529-variant-concern-Omicron-for-the-EU-EEA-Nov2021.pdf |url-status=live }}</ref>
As with other variants, the WHO recommended that people continue to keep enclosed spaces well ventilated, [[Social distancing measures related to the COVID-19 pandemic|avoid crowding and close contact]], wear well-fitting masks, clean hands frequently, and get vaccinated.<ref name="who-statement" /><ref name="reuters">{{cite news |date=26 November 2021 |title=WHO names new COVID variant omicron, cautions against travel measures |work=[[Reuters]] |url=https://www.reuters.com/business/healthcare-pharmaceuticals/who-meeting-friday-designate-new-variant-b11529-2021-11-26/ |url-status=live |access-date=26 November 2021 |archive-url=https://web.archive.org/web/20211126192036/https://www.reuters.com/business/healthcare-pharmaceuticals/who-meeting-friday-designate-new-variant-b11529-2021-11-26/ |archive-date=26 November 2021 |vauthors=Nebehay S, Winning A}}</ref> On 29 November 2021, the WHO said cases and infections were expected among those vaccinated, albeit in a small and predictable proportion.<ref name="who-very-high-risk">{{cite news |date=29 November 2021 |title=Omicron poses very high global risk, world must prepare -WHO |work=Reuters |location=Geneva |url=https://www.reuters.com/business/healthcare-pharmaceuticals/omicron-poses-very-high-global-risk-countries-must-prepare-who-2021-11-29/ |url-status=live |access-date=30 November 2021 |archive-url=https://web.archive.org/web/20211130173913/https://www.reuters.com/business/healthcare-pharmaceuticals/omicron-poses-very-high-global-risk-countries-must-prepare-who-2021-11-29/ |archive-date=30 November 2021}}</ref>

=== International response ===
After the WHO announcement, on the same day, several countries announced travel bans from southern Africa in response to the identification of the variant, including the [[United States]], which banned travel from eight African countries,<ref>{{Cite news |date=28 November 2021 |title=Covid live updates today: Omicron variant, symptoms, vaccines efficacy, restrictions... |work=en.as |url=https://en.as.com/en/2021/11/28/latest_news/1638109908_212481.html |url-status=live |access-date=28 November 2021 |archive-url=https://web.archive.org/web/20211128215231/https://en.as.com/en/2021/11/28/latest_news/1638109908_212481.html |archive-date=28 November 2021}}</ref> although as of 30 November 2021 it notably did not ban travel from any European countries, Israel, Canada, or Australia where cases were also detected at the time the bans were announced. Other countries that also implemented travel bans include Japan, Canada, the European Union, Israel, Australia, the United Kingdom, Singapore, Malaysia, Indonesia, Morocco, and New Zealand.<ref>{{cite news |date=30 November 2021 |title=World closing its doors to African countries due to omicron |work=aa.com |url=https://www.aa.com.tr/en/americas/world-closing-its-doors-to-african-countries-due-to-omicron/2434131 |url-status=live |access-date=30 November 2021 |archive-url=https://web.archive.org/web/20211130210038/https://www.aa.com.tr/en/americas/world-closing-its-doors-to-african-countries-due-to-omicron/2434131 |archive-date=30 November 2021}}</ref><ref>{{cite news |date=26 November 2021 |title=Singapore bans travellers from 7 African countries; no cases of new Covid-19 variant here |newspaper=The Straits Times |location=Singapore |url=https://www.straitstimes.com/singapore/spore-tightens-border-measures-for-travellers-from-7-african-countries-no-cases-of-new |url-status=live |access-date=26 November 2021 |archive-url=https://web.archive.org/web/20211126064129/https://www.straitstimes.com/singapore/spore-tightens-border-measures-for-travellers-from-7-african-countries-no-cases-of-new |archive-date=26 November 2021 |vauthors=Yong C}}</ref>

On 26 November 2021 the [[Brazilian Health Regulatory Agency]] recommended flight restrictions regarding the new variant.<ref>{{Cite web |date=26 November 2021 |title=Anvisa recomenda restrições de voo diante de nova variante de covid-19 |trans-title=Anvisa recommends flight restrictions in view of the new covid-19 variant |url=https://agenciabrasil.ebc.com.br/saude/noticia/2021-11/anvisa-recomenda-restricoes-de-voo-diante-de-nova-variante-de-covid-19 |archive-url=https://web.archive.org/web/20211126231213/https://agenciabrasil.ebc.com.br/saude/noticia/2021-11/anvisa-recomenda-restricoes-de-voo-diante-de-nova-variante-de-covid-19 |archive-date=26 November 2021 |access-date=27 November 2021 |work=agenciabrasil.ebc.com.br}}</ref> The [[COVID-19 pandemic in New York (state)|state of New York]] declared a state of emergency ahead of a potential Omicron spike, although no cases had yet been detected in the state or the rest of the United States.<ref>{{Cite web |title='It's Coming': NY Declares State of Emergency Ahead of Potential Omicron Spike |url=https://www.nbcnewyork.com/news/local/omicron-variant-ny-declares-state-of-emergency-ahead-of-potential-spike/3421297/ |url-status=live |archive-url=https://web.archive.org/web/20211126235057/https://www.nbcnewyork.com/news/local/omicron-variant-ny-declares-state-of-emergency-ahead-of-potential-spike/3421297/ |archive-date=26 November 2021 |access-date=27 November 2021 |website=NBC New York |vauthors=Kennedy M, Price RD|date=26 November 2021 }}</ref> On 27 November 2021, Switzerland introduced obligatory tests and quarantine for all visitors arriving from countries where the variant was detected, which originally included Belgium and Israel.<ref>{{cite news |title=Switzerland announces new restrictions for Israelis after the discovery of Omicron |work=Globally 24 |url=https://globally24.com/switzerland-announces-new-restrictions-for-israelis-after-the-discovery-of-omicron/ |url-status=live |access-date=27 November 2021 |archive-url=https://web.archive.org/web/20211127202928/https://globally24.com/switzerland-announces-new-restrictions-for-israelis-after-the-discovery-of-omicron/ |archive-date=27 November 2021}}</ref>

On 26 November 2021, South African [[Minister of Health (South Africa)|Minister of Health]] [[Joe Phaahla]] defended his country's handling of the pandemic and said that travel bans went against the "norms and standards" of the World Health Organization.<ref>{{cite news |date=26 November 2021 |title=South Africa says travel bans over new variant unjustified |work=[[Reuters]] |url=https://www.reuters.com/world/south-africa-calls-british-travel-ban-over-new-covid-19-variant-rushed-2021-11-26/ |url-status=live |access-date=26 November 2021 |archive-url=https://web.archive.org/web/20211126120245/https://www.reuters.com/world/south-africa-calls-british-travel-ban-over-new-covid-19-variant-rushed-2021-11-26/ |archive-date=26 November 2021 |vauthors=Winning A, Cocks T}}</ref>

Some speculated that [[COVID-19 travel restrictions|travel bans]] could have a significant impact on South Africa's economy by limiting tourism and could lead to other countries with economies that are reliant on tourism to hide the discovery of new variants of concern. [[vaccine inequity|Low vaccine coverage in less-developed nations]] could create opportunities for the emergence of new variants, and these nations also were struggling to gain [[TRIPS Waiver|intellectual property to develop and produce vaccines]] locally.<ref>{{Cite web |title=Travel bans aren't the answer to stopping new COVID variant Omicron |url=http://theconversation.com/travel-bans-arent-the-answer-to-stopping-new-covid-variant-omicron-172736 |url-status=live |archive-url=https://web.archive.org/web/20211128063613/https://theconversation.com/travel-bans-arent-the-answer-to-stopping-new-covid-variant-omicron-172736 |archive-date=28 November 2021 |access-date=28 November 2021 |website=The Conversation |vauthors=Zwi A|date=28 November 2021 }}</ref> At the same time, [[inoculation]] had slowed in South Africa due to [[vaccine hesitancy]] and apathy, with a nationwide vaccination rate of only 35% as of 24 November 2021.<ref>{{cite news |date=24 November 2021 |title=EXCLUSIVE South Africa delays COVID vaccine deliveries as inoculations slow |work=Reuters |url=https://www.reuters.com/world/africa/exclusive-south-africa-delays-covid-vaccine-deliveries-inoculations-slow-2021-11-24/ |url-status=live |access-date=28 November 2021 |archive-url=https://web.archive.org/web/20211128023919/https://www.reuters.com/world/africa/exclusive-south-africa-delays-covid-vaccine-deliveries-inoculations-slow-2021-11-24/ |archive-date=28 November 2021}}</ref>

On 29 November 2021, the WHO warned countries that the variant poses a very high global risk with severe consequences and that they should prepare by accelerating vaccination of high-priority groups and [[Health system strengthening|strengthening health systems]]. WHO director-general Tedros Adhanom described the global situation as dangerous and precarious and called for a new agreement on the handling of pandemics, as the <q>current system disincentivizes countries from alerting others to threats that will inevitably land on their shores.</q> [[Coalition for Epidemic Preparedness Innovations|CEPI]] CEO [[Richard Hatchett]] said that the variant fulfilled predictions that transmission of the virus in low-vaccination areas would accelerate its evolution.<ref name="who-very-high-risk" />

In preparation for the Omicron variant arriving in the United States, President [[Joe Biden]] stated that the variant is "cause for concern, not panic", reiterated that the government was prepared for the variant and would have it under control and that large-scale lockdowns, similar to the ones in 2020 near the beginning of the pandemic, were "off the table for now."<ref>{{Cite web |author=Kaitlan Collins and Kate Sullivan |title=Biden says new Omicron variant is 'cause for concern, not a cause for panic' |url=https://www.cnn.com/2021/11/29/politics/omicron-variant-covid-19-joe-biden/index.html |url-status=live |archive-url=https://web.archive.org/web/20211202011430/https://www.cnn.com/2021/11/29/politics/omicron-variant-covid-19-joe-biden/index.html |archive-date=2 December 2021 |access-date=1 December 2021 |website=CNN|date=29 November 2021 }}</ref>

In December 2021, multiple Canadian provinces reinstated restrictions on gatherings and events such as sports tournaments, and tightened enforcement of [[proof of vaccination]] orders. British Columbia expressly prohibited any non-seated "organized New Year's Eve event",<ref>{{Cite web |date=20 December 2021 |title=New COVID-19 restrictions in effect for parts of Canada; some productions cancelled |url=https://www.ctvnews.ca/canada/new-covid-19-restrictions-in-effect-for-parts-of-canada-some-productions-cancelled-1.5713852 |url-status=live |archive-url=https://web.archive.org/web/20211220224055/https://www.ctvnews.ca/canada/new-covid-19-restrictions-in-effect-for-parts-of-canada-some-productions-cancelled-1.5713852 |archive-date=20 December 2021 |access-date=20 December 2021 |website=CTVNews }}</ref><ref>{{Cite web |title=B.C. enacts social gathering and event capacity limits as Omicron variant spreads |url=https://globalnews.ca/news/8459081/bc-covid-update-new-rules-omicron-dec-17-2021/ |url-status=live |archive-url=https://web.archive.org/web/20211219201516/https://globalnews.ca/news/8459081/bc-covid-update-new-rules-omicron-dec-17-2021/ |archive-date=19 December 2021 |access-date=18 December 2021 |website=Global News}}</ref><ref>{{Cite web |date=17 December 2021 |title=B.C. limits indoor gatherings, cancels New Year's Eve events as Omicron picks up speed |url=https://www.cbc.ca/news/canada/british-columbia/british-columbia-covid-restrictions-1.6290309 |url-status=live |archive-url=https://web.archive.org/web/20211220200248/https://www.cbc.ca/news/canada/british-columbia/british-columbia-covid-restrictions-1.6290309 |archive-date=20 December 2021 |access-date=17 December 2021 |website=CBC News}}</ref> while Quebec announced a partial lockdown on 20 December 2021, ordering the closure of all bars, casinos, gyms, schools, and theatres, as well as imposing restrictions on the capacity and operating hours of restaurants, and the prohibition of spectators at professional sporting events.<ref>{{Cite web |date=20 December 2021 |title=Quebec shutting down schools, bars, gyms tonight as COVID-19 cases soar |url=https://montreal.ctvnews.ca/quebec-shutting-down-schools-bars-gyms-tonight-as-covid-19-cases-soar-1.5714268 |url-status=live |archive-url=https://web.archive.org/web/20211220200903/https://montreal.ctvnews.ca/quebec-shutting-down-schools-bars-gyms-tonight-as-covid-19-cases-soar-1.5714268 |archive-date=20 December 2021 |access-date=20 December 2021 |website=CTV News Montreal }}</ref>

On 18 December 2021, the Netherlands government announced a lockdown intended to prevent spread of the variant during the holiday period.<ref>{{Cite news |date=18 December 2021 |title=Netherlands to go into strict Christmas lockdown |work=Reuters |url=https://www.reuters.com/business/healthcare-pharmaceuticals/netherlands-set-announce-strict-christmas-lockdown-media-2021-12-18/ |url-status=live |access-date=2 January 2022 |archive-url=https://web.archive.org/web/20220102160427/https://www.reuters.com/business/healthcare-pharmaceuticals/netherlands-set-announce-strict-christmas-lockdown-media-2021-12-18/ |archive-date=2 January 2022 |vauthors=Meijer BH, van den Berg S}}</ref>

In December 2021, some countries shortened the typical six-month interval for a booster dose of the vaccine to prepare for a wave of Omicron, as two doses are not enough to stop the infection. UK, South Korea and Thailand reduced to three months; Belgium, four months; France, Singapore, Taiwan, Italy and Australia, five months. Finland reduced it to three months for risk groups. Other countries continued with a six-month booster schedule. While antibody levels begin to drop at four months, a longer interval usually allows time for the immune system's response to mature.<ref>{{cite news |date=20 December 2022 |title=As Omicron threatens a global surge, some countries shorten COVID-19 booster timelines |work=Reuters |url=https://www.reuters.com/business/healthcare-pharmaceuticals/omicron-threatens-global-surge-some-countries-shorten-covid-19-booster-timelines-2021-12-20/ |url-status=live |access-date=15 January 2022 |archive-url=https://web.archive.org/web/20220115145917/https://www.reuters.com/business/healthcare-pharmaceuticals/omicron-threatens-global-surge-some-countries-shorten-covid-19-booster-timelines-2021-12-20/ |archive-date=15 January 2022}}</ref>

== Biology ==
[[File:SARS-CoV-2 Omicron (BA.1) variant.svg|none|thumb|900px|{{Center|The genomic sequence of the Omicron variant is pictured above|style=margin:0;padding:0;}}]]

=== Mutations ===
As of June 2022, Omicron had about 50 mutations relative to the Wuhan-Hu-1 or B variant,<ref>{{cite web | url=https://virological.org/t/selection-analysis-identifies-significant-mutational-changes-in-omicron-that-are-likely-to-influence-both-antibody-neutralization-and-spike-function-part-1-of-2/771 | title=Selection analysis identifies significant mutational changes in Omicron that are likely to influence both antibody neutralization and Spike function (Part 1 of 2) | date=5 December 2021 | access-date=1 December 2023 | archive-date=17 November 2023 | archive-url=https://web.archive.org/web/20231117224648/https://virological.org/t/selection-analysis-identifies-significant-mutational-changes-in-omicron-that-are-likely-to-influence-both-antibody-neutralization-and-spike-function-part-1-of-2/771 | url-status=live }}</ref><ref>{{cite journal | url=https://karger.com/che/article/66/1-2/3/78103/SARS-CoV-2-Lineages-and-Sub-Lineages-Circulating | doi=10.1159/000515340 | title=SARS-CoV-2 Lineages and Sub-Lineages Circulating Worldwide: A Dynamic Overview | date=2021 | vauthors = Cella E, Benedetti F, Fabris S, Borsetti A, Pezzuto A, Ciotti M, Pascarella S, Ceccarelli G, Zella D, Ciccozzi M, Giovanetti M | journal=Chemotherapy | volume=66 | issue=1–2 | pages=3–7 | pmid=33735881 | pmc=8089399 | access-date=1 December 2023 | archive-date=29 October 2023 | archive-url=https://web.archive.org/web/20231029152043/https://karger.com/che/article/66/1-2/3/78103/SARS-CoV-2-Lineages-and-Sub-Lineages-Circulating | url-status=live }}</ref> which is more than any previous [[Variants of SARS-CoV-2|SARS-CoV-2 variant]]. Thirty-two of these pertained to the spike protein, which most [[COVID-19 vaccine|vaccines]] target to neutralise the virus.<ref>{{cite journal |vauthors=Khandia R, Singhal S, Alqahtani T, Kamal MA, El-Shall NA, Nainu F, Desingu PA, Dhama K |date=June 2022 |title=Emergence of SARS-CoV-2 Omicron (B.1.1.529) variant, salient features, high global health concerns and strategies to counter it amid ongoing COVID-19 pandemic |journal=Environmental Research |volume=209 |page=112816 |bibcode= 2022ER....20912816K|doi=10.1016/j.envres.2022.112816 |pmc=8798788 |pmid=35093310}}</ref> As of December 2021, many mutations were novel and not found in previous variants.<ref name="nature-alert" /> As of April 2022 the variant was characterised by 30 [[amino acid]] changes, three small deletions, and one small insertion in the spike protein compared with the original virus, of which 15 are located in the receptor-binding domain (residues 319–541).<ref>{{cite journal |vauthors=Hong Q, Han W, Li J, Xu S, Wang Y, Xu C, Li Z, Wang Y, Zhang C, Huang Z, Cong Y |date=April 2022 |title=Molecular basis of receptor binding and antibody neutralization of Omicron |journal=Nature |volume=604 |issue=7906 |pages=546–552 |bibcode=2022Natur.604..546H |doi=10.1038/s41586-022-04581-9 |pmid=35228716 |s2cid=247167987|doi-access = free | title-link = doi }}</ref> As of December 2022 the virus carried a number of changes and deletions in other genomic regions. For example, three mutations at the [[furin]] [[proteolytic cleavage site|cleavage site]], which facilitates its transmission.<ref>{{cite journal |vauthors=Mileto D, Micheli V, Fenizia C, Cutrera M, Gagliardi G, Mancon A, Bracchitta F, De Silvestri A, Rizzardini G, Lombardi A, Biasin M, Gismondo MR |date=December 2022 |title=Reduced neutralization of SARS-CoV-2 Omicron variant by BNT162b2 vaccinees' sera: a preliminary evaluation |journal=Emerging Microbes & Infections |volume=11 |issue=1 |pages=790–792 |doi=10.1080/22221751.2022.2045878 |pmc=8920392 |pmid=35196967}}</ref><ref>{{cite journal |vauthors=Zhang L, Mann M, Syed ZA, Reynolds HM, Tian E, Samara NL, Zeldin DC, Tabak LA, Ten Hagen KG |date=November 2021 |title=Furin cleavage of the SARS-CoV-2 spike is modulated by ''O''-glycosylation |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=118 |issue=47 |pages=e2109905118 |bibcode=2021PNAS..11809905Z |doi=10.1073/pnas.2109905118 |pmc=8617502 |pmid=34732583 |doi-access = free | title-link = doi |s2cid=242937417}}</ref>
{{multiple image
| image1            = Spike omicron mutations top.png
| alt1              = Spike protein with mutations highlighted, looking down onto the receptor-binding domain
| image2            = Spike omicron mutations side.png
| alt2              = Spike protein with mutations highlighted, looking at the side of the protein
| footer            = Illustration of the locations of the Omicron mutations in the [[coronavirus spike protein|spike protein]], top view (left) and side view (right), showing amino acid [[substitution mutation|substitutions]] (yellow), [[deletion mutation|deletions]] (red), and [[insertion mutation|insertions]] (green). In this trimeric structure, two monomers (gray and light blue) have their receptor-binding domains in the "down" conformation while one (dark blue) is in the "up" or "open" conformation. Mutation data from the [[WHO]],<ref name="who-statement">{{Cite web|date=26 November 2021|title=Classification of Omicron (B.1.1.529): SARS-CoV-2 Variant of Concern|url=https://www.who.int/news/item/26-11-2021-classification-of-omicron-(b.1.1.529)-sars-cov-2-variant-of-concern|url-status=live|access-date=26 November 2021|website=World Health Organization|archive-date=26 November 2021|archive-url=https://web.archive.org/web/20211126180836/https://www.who.int/news/item/26-11-2021-classification-of-omicron-%28b.1.1.529%29-sars-cov-2-variant-of-concern}}</ref> structure from {{PDB|6VYB}}.<ref name="walls_2020">{{cite journal | vauthors = Walls AC, Park YJ, Tortorici MA, Wall A, McGuire AT, Veesler D | title = Structure, Function, and Antigenicity of the SARS-CoV-2 Spike Glycoprotein | journal = Cell | volume = 181 | issue = 2 | pages = 281–292.e6 | date = April 2020 | pmid = 32155444 | pmc = 7102599 | doi = 10.1016/j.cell.2020.02.058 }}</ref>
| align             = left
}}

[[File:Mutation prevalence across Omicron lineages.jpg|alt=Mutation prevalence across Omicron lineages|thumb|350px|Comparison of mutation prevalence for ORF1a, ORF1b, and S genes of Omicron lineages that are designated Variants of Concern. Characteristic mutations for a lineage are defined as nonsynonymous substitutions or deletions that occur in > 75% of sequences within that lineage.<ref>{{Cite web |author=Karthik Gangavarapu |author2=Alaa Abdel Latif |author3=Julia Mullen |author4=Manar Alkuzweny |author5=Emory Hufbauer |author6=Ginger Tsueng |author7=Emily Haag |author8=Mark Zeller |author9=Christine M. Aceves |date=18 August 2022 |title=Lineage Comparison |url=https://outbreak.info/compare-lineages |website=Outbreak.info |author10=Karina Zaiets |author11=Marco Cano |author12=Jerry Zhou |author13=Zhongchao Qian |author14=Rachel Sattler |author15=Nathaniel L Matteson |author16=Joshua I. Levy |author17=Raphael TC Lee |author18=Lucas Freitas |author19=Sebastian Maurer-Stroh |author20=GISAID core and curation team |author21=Marc A. Suchard |author22=Chunlei Wu |author23=Andrew I. Su |author24=Kristian G. Andersen |author25=Laura D. Hughes |author26=Center for Viral Systems Biology |access-date=24 August 2022 |archive-date=24 June 2021 |archive-url=https://web.archive.org/web/20210624204231/https://outbreak.info/compare-lineages |url-status=live }}</ref>|right]]
{{clear}}

== {{anchor|BA.1.1}}Subvariants ==
{{Main|Variants of SARS-CoV-2#Omicron}}
Several subvariants of Omicron have been discovered and new ones continue to emerge.<ref name=":0a" /> There are 310 Pango lineages{{clarify|date=February 2023}} currently associated with the Omicron variant.<ref>{{Cite web |author=Karthik Gangavarapu |author2=Alaa Abdel Latif |author3=Julia Mullen |author4=Manar Alkuzweny |author5=Emory Hufbauer |author6=Ginger Tsueng |author7=Emily Haag |author8=Mark Zeller |author9=Christine M. Aceves |date=19 August 2022 |title=Omicron Variant Report |url=https://outbreak.info/situation-reports/omicron |website=Outbreak.info |author10=Karina Zaiets |author11=Marco Cano |author12=Jerry Zhou |author13=Zhongchao Qian |author14=Rachel Sattler |author15=Nathaniel L Matteson |author16=Joshua I. Levy |author17=Raphael TC Lee |author18=Lucas Freitas |author19=Sebastian Maurer-Stroh |author20=GISAID core and curation team |author21=Marc A. Suchard |author22=Chunlei Wu |author23=Andrew I. Su |author24=Kristian G. Andersen |author25=Laura D. Hughes |author26=Center for Viral Systems Biology |access-date=24 August 2022 |archive-date=20 August 2022 |archive-url=https://web.archive.org/web/20220820013601/https://outbreak.info/situation-reports/omicron |url-status=live }}</ref> The 'standard' sublineage is now referred to as BA.1 (or B.1.1.529.1), and the two other sublineages are known as BA.2 (or B.1.1.529.2) and BA.3 (or B.1.1.529.3).<ref>{{cite journal |vauthors=Arora P, Zhang L, Rocha C, Sidarovich A, Kempf A, Schulz S, Cossmann A, Manger B, Baier E, Tampe B, Moerer O, Dickel S, Dopfer-Jablonka A, Jäck HM, Behrens GM, Winkler MS, Pöhlmann S, Hoffmann M |date=June 2022 |title=Comparable neutralisation evasion of SARS-CoV-2 omicron subvariants BA.1, BA.2, and BA.3 |journal=The Lancet. Infectious Diseases |volume=22 |issue=6 |pages=766–767 |doi=10.1016/S1473-3099(22)00224-9 |pmc=9005119 |pmid=35427493}}</ref> In 2022, BA.4 (or B.1.1.529.4) and BA.5 (or B.1.1.529.5) were detected in several countries.<ref>{{cite journal |vauthors=Mohapatra RK, Kandi V, Sarangi AK, Verma S, Tuli HS, Chakraborty S, Chakraborty C, Dhama K |date=July 2022 |title=The recently emerged BA.4 and BA.5 lineages of Omicron and their global health concerns amid the ongoing wave of COVID-19 pandemic - Correspondence |journal=International Journal of Surgery |volume=103 |page=106698 |doi=10.1016/j.ijsu.2022.106698 |pmc=9176102 |pmid=35690362}}</ref> They share many mutations, but also significantly differ. In general, BA.1 and BA.2 share 32 mutations, but differ by 28.<ref name="For 21Jan2022">{{cite news |date=21 January 2022 |title=What is 'stealth Omicron'? The rise of the subvariant is alarming some scientists who say it needs its own Greek letter |publisher=Fortune |url=https://fortune.com/2022/01/21/what-is-stealth-omicron-new-covid-variant-substrain-denmark/ |url-status=live |access-date=23 January 2022 |archive-url=https://web.archive.org/web/20220123050305/https://fortune.com/2022/01/21/what-is-stealth-omicron-new-covid-variant-substrain-denmark/ |archive-date=23 January 2022 |vauthors=McGregor G}}</ref> BA.1 has itself been divided in two, the original BA.1 and BA.1.1 (or B.1.1.529.1.1) where the main difference is that the latter has a R346K mutation.<ref>{{cite journal |vauthors=Vauhkonen H, Nguyen PT, Kant R, Plyusnin I, Erdin M, Kurkela S, Liimatainen H, Ikonen N, Blomqvist S, Liitsola K, Lindh E, Helve O, Jarva H, Loginov R, Palva A, Hannunen T, Hannula S, Parry M, Kauppi P, Vaheri A, Sironen T, Lappalainen M, Savolainen-Kopra C, Smura T, Vapalahti O |date=June 2022 |title=Introduction and Rapid Spread of SARS-CoV-2 Omicron Variant and Dynamics of BA.1 and BA.1.1 Sublineages, Finland, December 2021 |journal=Emerging Infectious Diseases |volume=28 |issue=6 |pages=1229–1232 |doi=10.3201/eid2806.220515 |pmc=9155872 |pmid=35378057}}</ref>

Standard [[Polymerase chain reaction|PCR]] and [[COVID-19 rapid antigen test|rapid]] tests continue to detect all Omicron subvariants as COVID-19, but further tests are necessary to distinguish the subvariants from each other and from other COVID-19 variants.<ref>{{cite journal |vauthors=Rahimi F, Talebi Bezmin Abadi A |date=March 2022 |title=The Omicron subvariant BA.2: Birth of a new challenge during the COVID-19 pandemic |journal=International Journal of Surgery |volume=99 |page=106261 |doi=10.1016/j.ijsu.2022.106261 |pmc=8837492 |pmid=35167986}}</ref>

{| class="wikitable mw-collapsible autocollapse" style="text-align: left; padding-right:1em;margin-right:1em" align="left"
 |+ {{nowrap|Defining mutations in the<br />SARS-CoV-2 Omicron variant{{Break}} }}
 ! [[Gene]]
 ! [[Amino acid]]
 |-
 ! rowspan="11" | [[ORF1ab]]
 |   |nsp3: K38R
|-
 |   |nsp3: V1069I
|-
 |   |nsp3: Δ1265
|-
 |   |nsp3: L1266I
|-
 |   |nsp3: A1892T
|-
 |   |nsp4: T492I
|-
 |   |nsp5: P132H
|-
 |   |nsp6: Δ105-107
|-
 |   |nsp6: A189V
|-
 |   |nsp12: P323L
|-
 |   |nsp14: I42V
|-
 ! rowspan="34" | [[coronavirus spike protein|Spike]]
  |  | A67V
|-
 |  | Δ69-70
|-
 |  | T95I
|-
 |  | G142D,
|-
 |  | Δ143-145
|-
 |  | Δ211
|-
 |  | L212I
|-
 |  | ins214EPE
|-
 |  | G339D
|-
 |  | S371L
|-
 |  | S373P
|-
 |  | S375F
|-
 |  | K417N
|-
 |  | N440K
|-
 |  | G446S
|-
 |  | S477N
|-
 |  | T478K
|-
 |  | E484A
|-
 |  | Q493R
|-
 |  | G496S
|-
 |  | Q498R
|-
 |  | N501Y
|-
 |  | Y505H
|-
 |  | T547K
|-
 |  | D614G
|-
 |  | H655Y
|-
 |  | N679K
|-
 |  | P681H
|-
 |  | N764K
|-
 |  | D796Y
|-
 |  | N856K
|-
 |  | Q954H
|-
 |  | N969K
|-
 |  | L981F
 |-
 ! rowspan="1" | [[Coronavirus envelope protein|E]]
 |  | T9I
 |-
 ! rowspan="3" | [[coronavirus membrane protein|M]]
 |  | D3G
 |-
 |  | Q19E
 |-
 |  | A63T
 |-
 ! rowspan="4" | [[coronavirus nucleocapsid protein|N]]
 |  | P13L
 |-
 |  | Δ31-33
 |-
 |  | R203K
 |-
 |  | G204R
 |-
|
 |- style="text-align:left;" class="sortbottom"
 | colspan="2" | Sources: UK Health Security Agency<ref>{{cite web |url=https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1036501/Technical_Briefing_29_published_26_November_2021.pdf |title=SARS-CoV-2 variants of concern and variants under investigation in England – Technical briefing 29 |date=26 November 2021 |website=gov.uk |publisher=UK Health Security Agency |page=18 |access-date=10 December 2021 |archive-date=27 November 2021 |archive-url=https://web.archive.org/web/20211127004349/https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1036501/Technical_Briefing_29_published_26_November_2021.pdf |url-status=live }}</ref> CoVariants<ref name="CoVariants1" />
|}

=== {{anchor|SV-BA.1}}BA.2 ===
BA.2 was first detected in a sample from 15 November 2021.<ref>{{cite web |date=4 February 2022 |title=BA.2 Lineage Report, India |url=https://outbreak.info/situation-reports?pango=BA.2&selected=IND&loc=IND&overlay=false |access-date=5 February 2022 |publisher=outbreak.info ([[Scripps Research]]) |archive-date=5 February 2022 |archive-url=https://web.archive.org/web/20220205204024/https://outbreak.info/situation-reports?pango=BA.2&selected=IND&loc=IND&overlay=false |url-status=live }}</ref> A preprint released in February 2022 (published in May) suggested that BA.2 was more transmissible than BA.1 and may cause more severe disease.<ref>{{Cite journal | vauthors = Yamasoba D, Kimura I, Nasser H, Morioka Y, Nao N, Ito J, Uriu K, Tsuda M, Zahradnik J, Shirakawa K, Suzuki R, etal | journal = Cell |date=9 June 2022 |title=Virological characteristics of the SARS-CoV-2 Omicron BA.2 spike |biorxiv=10.1101/2022.02.14.480335v1 |volume=185 |issue=12 |pages=2103–2115 |doi=10.1016/j.cell.2022.04.035 | pmid = 35568035 | pmc = 9057982 | s2cid = 246905491 }}</ref> This was later disproven by a study in late-October 2022, that found BA.2 actually caused less severe disease relative to BA.1 (which in turn, caused less severe disease compared to the delta variant).<ref>{{Cite web |date=31 October 2022 |title=SARS-CoV-2 Omicron BA.2 less severe than Delta and original Omicron |first=Bhavana |last=Kunkalikar |name-list-style=vanc |url=https://www.news-medical.net/news/20221031/SARS-CoV-2-Omicron-BA2-less-severe-than-Delta-and-original-Omicron.aspx |access-date=6 November 2022 |website=News-Medical.net |archive-date=6 November 2022 |archive-url=https://web.archive.org/web/20221106035310/https://www.news-medical.net/news/20221031/SARS-CoV-2-Omicron-BA2-less-severe-than-Delta-and-original-Omicron.aspx |url-status=live }}</ref> Therapeutic monoclonal antibodies used to treat people infected with COVID-19 did not have much effect on BA.2, which was "almost completely resistant" to casirivimab and imdevimab, and 35 times more resistant to sotrovimab than the BA.1 subvariant.{{citation needed|date=August 2023}}

==== Spread ====
As of 17 January 2022, BA.2 had been detected in at least 40 countries and in all continents except Antarctica.<ref name="OBI BA2">{{cite web |date=21 January 2022 |title=BA.2 Lineage Report |url=https://outbreak.info/situation-reports?pango=BA.2 |url-status=live |archive-url=https://web.archive.org/web/20211213170850/https://outbreak.info/situation-reports?pango=BA.2 |archive-date=13 December 2021 |access-date=21 January 2022 |publisher=outbreak.info ([[Scripps Research]])}}</ref> By 31 January, it had been detected in at least 57 countries.<ref>{{cite web |date=1 February 2022 |title=COVID-19 Weekly Epidemiological Update, Edition 77 |url=https://www.who.int/docs/default-source/coronaviruse/situation-reports/20220201_weekly_epi_update_77.pdf |url-status=live |archive-url=https://web.archive.org/web/20220203200935/https://www.who.int/docs/default-source/coronaviruse/situation-reports/20220201_weekly_epi_update_77.pdf |archive-date=3 February 2022 |publisher=World Health Organization |access-date=2 February 2022}}</ref> In global samples collected from 4 February to 5 March and uploaded to [[GISAID]], BA.2 accounted for c. 34%, compared to 41% for BA.1.1, 25% for BA.1 and less than 1% for BA.3.<ref name="WHO edition82">{{cite web |date=8 March 2022 |title=COVID-19 Weekly Epidemiological Update, Edition 82 |url=https://www.who.int/publications/m/item/weekly-epidemiological-update-on-covid-19---8-march-2022 |publisher=World Health Organization |access-date=12 March 2022 |archive-date=13 March 2022 |archive-url=https://web.archive.org/web/20220313061107/https://www.who.int/publications/m/item/weekly-epidemiological-update-on-covid-19---8-march-2022 |url-status=live }}</ref> In a review two weeks later, covering 16 February to 17 March, BA.2 had become the most frequent.<ref name="WHO edition84">{{cite web |date=22 March 2022 |title=COVID-19 Weekly Epidemiological Update, Edition 84 |url=https://www.who.int/publications/m/item/weekly-epidemiological-update-on-covid-19---22-march-2022 |publisher=World Health Organization |access-date=25 March 2022 |archive-date=26 March 2022 |archive-url=https://web.archive.org/web/20220326055351/https://www.who.int/publications/m/item/weekly-epidemiological-update-on-covid-19---22-march-2022 |url-status=live }}</ref><ref>{{cite news |date=22 March 2022 |title=How fast omicron's BA.2 variant is spreading around the world |newspaper=Washington Post |url=https://www.washingtonpost.com/health/interactive/2021/tracker-omicron-spread/ |access-date=24 March 2022 |vauthors=Keating D, Dong M, Shin Y |archive-date=23 March 2022 |archive-url=https://web.archive.org/web/20220323210111/https://www.washingtonpost.com/health/interactive/2021/tracker-omicron-spread/ |url-status=live }}</ref> Based on GISAID uploads, BA.1 peaked in January 2022, after which it was overtaken by both BA.1.1 and BA.2.<ref name="WHO edition80">{{cite web |date=22 February 2022 |title=COVID-19 Weekly Epidemiological Update, Edition 80 |url=https://www.who.int/publications/m/item/weekly-epidemiological-update-on-covid-19---22-february-2022 |publisher=World Health Organization |access-date=12 March 2022 |archive-date=10 March 2022 |archive-url=https://web.archive.org/web/20220310184040/https://www.who.int/publications/m/item/weekly-epidemiological-update-on-covid-19---22-february-2022 |url-status=live }}</ref> In North America, parts of Europe and parts of Asia, BA.1 was first outcompeted by BA.1.1. For example, in the United States, France and Japan, BA.1.1 became the dominant subvariant in January 2022.<ref name="CDC Variants">{{cite web |date=28 March 2020 |title=Variant Proportions |url=https://covid.cdc.gov/covid-data-tracker/#variant-proportions |publisher=Centers for Disease Control and Prevention |access-date=12 March 2022 |archive-date=24 August 2020 |archive-url=https://web.archive.org/web/20200824224244/https://covid.cdc.gov/covid-data-tracker/#variant-proportions |url-status=live }}</ref><ref>{{cite news |date=7 February 2022 |title=BA.1.1, un nouveau sous-variant d'Omicron déjà très répandu en France |publisher=Le Progrès |url=https://www.leprogres.fr/sante/2022/02/07/ba-1-1-un-nouveau-sous-variant-d-omicron-deja-tres-repandu-en-france |vauthors=Carassio J |access-date=12 March 2022 |archive-date=12 March 2022 |archive-url=https://web.archive.org/web/20220312021737/https://www.leprogres.fr/sante/2022/02/07/ba-1-1-un-nouveau-sous-variant-d-omicron-deja-tres-repandu-en-france |url-status=live }}</ref><ref name="OBI BA11">{{cite web |date=12 March 2022 |title=BA.1.1 Lineage Report, United States, France and Japan |url=https://outbreak.info/situation-reports?pango=BA.1.1&loc=USA&loc=FRA&loc=JPN&selected=JPN&overlay=false |access-date=12 March 2022 |publisher=outbreak.info ([[Scripps Research]]) |archive-date=14 March 2022 |archive-url=https://web.archive.org/web/20220314145334/https://outbreak.info/situation-reports?pango=BA.1.1&loc=USA&loc=FRA&loc=JPN&selected=JPN&overlay=false |url-status=live }}</ref>

By December 2021/January 2022, BA.2 had become dominant in parts of India (already making up almost 80 percent in [[Kolkata]] in December 2021<ref>{{cite news |date=11 January 2022 |title=BA.2 'stealth' variant makes up 80% of Kolkata's Omicron infections |work=The Times of India |url=https://timesofindia.indiatimes.com/city/kolkata/ba-2-stealth-variant-makes-up-80-of-kolkatas-o-infections/articleshow/88821640.cms |url-status=live |archive-url=https://web.archive.org/web/20220116044618/https://timesofindia.indiatimes.com/city/kolkata/ba-2-stealth-variant-makes-up-80-of-kolkatas-o-infections/articleshow/88821640.cms |archive-date=16 January 2022 |vauthors=Yengkhom S |access-date=17 January 2022}}</ref>) and the Philippines, had become frequent in Scandinavia, South Africa and Singapore, and was showing signs of growth in Germany and the United Kingdom.<ref>{{cite news |date=21 January 2022 |title=Omicron 'sub-lineage' BA.2 designated as COVID variant under investigation, says UKHSA |publisher=Sky News |url=https://news.sky.com/story/omicron-sub-lineage-ba-2-designated-as-covid-variant-under-investigation-says-ukhsa-12521718 |url-status=live |archive-url=https://web.archive.org/web/20220121211659/https://news.sky.com/story/omicron-sub-lineage-ba-2-designated-as-covid-variant-under-investigation-says-ukhsa-12521718 |archive-date=21 January 2022 |access-date=21 January 2022}}</ref><ref>{{Cite web |date=14 January 2022 |title=SARS-CoV-2 Sequencing Update 14 January 2022 |url=https://www.nicd.ac.za/wp-content/uploads/2022/01/Update-of-SA-sequencing-data-from-GISAID-14-Jan-2022.pdf |url-status=live |archive-url=https://web.archive.org/web/20220117175012/https://www.nicd.ac.za/wp-content/uploads/2022/01/Update-of-SA-sequencing-data-from-GISAID-14-Jan-2022.pdf |archive-date=17 January 2022 |access-date=17 January 2022 |publisher=Network for Genomic Surveillance in South Africa}}</ref><ref name="TheIndependent 23Jan2022">{{cite news |date=23 January 2022 |title=Omicron sub-variant BA.2 'under investigation' by UK health officials |work=The Independent |url=https://www.independent.co.uk/news/science/omicron-variant-ba2-latest-covid-b1998907.html |url-status=live |archive-url=https://web.archive.org/web/20220123115111/https://www.independent.co.uk/news/science/omicron-variant-ba2-latest-covid-b1998907.html |archive-date=23 January 2022 |access-date=23 January 2022}}</ref><ref>{{Cite news |date=11 January 2022 |title=Undergrupp av omikron ökar: "Kan vara ännu mer smittsam" |language=sv |publisher=Aftonbladet |url=https://www.aftonbladet.se/nyheter/a/Jxq0y4/undergrupp-av-omikron-okar-kan-vara-annu-mer-smittsam |url-status=live |access-date=17 January 2022 |archive-url=https://web.archive.org/web/20220111162511/https://www.aftonbladet.se/nyheter/a/Jxq0y4/undergrupp-av-omikron-okar-kan-vara-annu-mer-smittsam |archive-date=11 January 2022 |vauthors=Österman H}}</ref> In Japan, which has quarantine and detailed screening of all international travellers, as of 24 January, the vast majority of BA.2 had been detected in people that had arrived from India or the Philippines with cases going back at least to 1 December 2021 (far fewer BA.1 or other variants were detected among arrivals from the two countries in that period), but small numbers had also been detected in people arriving from other countries.<ref name="Jpn 14Jan2022">{{cite web |date=14 January 2022 |title=SARS-CoV-2の変異株B.1.1.529系統(オミクロン株)について(第6報) |url=https://www.niid.go.jp/niid/ja/2019-ncov/2551-cepr/10900-sars-cov-2-b-1-1-530.html |url-status=live |archive-url=https://web.archive.org/web/20220120162213/https://www.niid.go.jp/niid/ja/2019-ncov/2551-cepr/10900-sars-cov-2-b-1-1-530.html |archive-date=20 January 2022 |publisher=[[National Institute of Infectious Diseases (Japan)]] |language=Japanese |access-date=24 January 2022}}</ref><ref>{{cite web |date=20 January 2022 |title=新型コロナウイルス感染症(変異株)の患者等の発生について(空港検疫)) |url=https://www.mhlw.go.jp/stf/newpage_23512.html |url-status=live |archive-url=https://web.archive.org/web/20220120153500/https://www.mhlw.go.jp/stf/newpage_23512.html |archive-date=20 January 2022 |publisher=[[National Institute of Infectious Diseases (Japan)]] |language=Japanese |access-date=24 January 2022}}</ref><ref>{{cite web |date=24 January 2022 |title=新型コロナウイルス感染症(変異株)の患者等の発生について(空港検疫) |url=https://www.mhlw.go.jp/stf/newpage_23561.html |url-status=live |archive-url=https://web.archive.org/web/20220124084044/https://www.mhlw.go.jp/stf/newpage_23561.html |archive-date=24 January 2022 |publisher=[[National Institute of Infectious Diseases (Japan)]] |language=Japanese |access-date=24 January 2022}}</ref>

In Denmark, the first BA.2 was in a sample collected on 5 December 2021.<ref name="C19DK">{{Cite news |date=29 January 2022 |title=Genomic overview of SARS-CoV-2 in Denmark |publisher=Danish Covid-19 Genome Consortium |url=https://www.covid19genomics.dk/statistics |url-status=live |access-date=29 January 2022 |archive-url=https://web.archive.org/web/20211220072151/https://www.covid19genomics.dk/statistics |archive-date=20 December 2021}}</ref> By week fifty (13–19 December) it had started to increase, with BA.2 being at around 2 percent of sequenced cases compared to 46 percent BA.1 (remaining Delta). The frequency of both Omicron subvariants continued to increase throughout the last half of December; and by the end of the year BA.2 had reached 20 percent and BA.1 peaked at 72 percent. In January 2022, BA.1 began decreasing, whereas BA.2 continued its increase. By the second week of 2022, the frequency of the two was almost equal, both being near 50 percent.<ref name="C19DK" /> In the following week, BA.2 became clearly dominant in Denmark with 65 percent of new cases.<ref name="WaPo 25Jan2022">{{cite news |date=25 January 2022 |title=There's a new version of omicron but so far it doesn't appear to be more dangerous |newspaper=Washington Post |url=https://www.washingtonpost.com/health/2022/01/24/covid-omicron-ba2/ |url-status=live |archive-url=https://web.archive.org/web/20220125052641/https://www.washingtonpost.com/health/2022/01/24/covid-omicron-ba2/ |archive-date=25 January 2022 |vauthors=Bernstein L |access-date=25 January 2022}}</ref> Trends from the other Scandinavian countries, India, South Africa and the United Kingdom also showed that BA.2 was increasing in proportion to BA.1.<ref>{{cite web |date=21 January 2022 |title=Enhancing response to Omicron SARS-CoV-2 variant: Technical brief and priority actions for Member States |url=https://www.who.int/docs/default-source/coronaviruse/2022-01-21-global-technical-brief-and-priority-action-on-omicron-sars-cov-2-variant.pdf |url-status=live |archive-url=https://web.archive.org/web/20220127201118/https://www.who.int/docs/default-source/coronaviruse/2022-01-21-global-technical-brief-and-priority-action-on-omicron-sars-cov-2-variant.pdf |archive-date=27 January 2022 |publisher=World Health Organization |access-date=24 January 2022}}</ref><ref name="FHI wk2">{{cite web |date=19 January 2022 |title=COVID-19 Ukerapport – uke 2 |url=https://www.fhi.no/contentassets/8a971e7b0a3c4a06bdbf381ab52e6157/vedlegg/2022/ukerapport-uke-2-10.01---16.01.22.pdf |url-status=live |archive-url=https://web.archive.org/web/20220127201054/https://www.fhi.no/contentassets/8a971e7b0a3c4a06bdbf381ab52e6157/vedlegg/2022/ukerapport-uke-2-10.01---16.01.22.pdf |archive-date=27 January 2022 |publisher=[[Norwegian Institute of Public Health]] |language=no |access-date=25 January 2022}}</ref> In February 2022, it had become the dominant subvariant in South Africa, in February it had become dominant in Germany and in March it had become dominant in the United Kingdom.<ref>{{Cite news |first1=Alexander |last1=Winning |first2=Estelle |last2=Shirbon |name-list-style=vanc |date=10 February 2022 |title=Omicron BA.2 sub-variant dominant in S.Africa, says CDC |work=Reuters |url=https://www.reuters.com/business/healthcare-pharmaceuticals/omicron-ba2-sub-variant-dominant-safrica-says-cdc-2022-02-10/ |access-date=12 March 2022 |archive-date=12 March 2022 |archive-url=https://web.archive.org/web/20220312021737/https://www.reuters.com/business/healthcare-pharmaceuticals/omicron-ba2-sub-variant-dominant-safrica-says-cdc-2022-02-10/ |url-status=live }}</ref><ref>{{Cite web |date=10 March 2022 |title=Wöchentlicher Lagebericht des RKI zur Coronavirus-Krankheit-2019 (COVID-19) |url=https://www.rki.de/DE/Content/InfAZ/N/Neuartiges_Coronavirus/Situationsberichte/Wochenbericht/Wochenbericht_2022-03-10.pdf |access-date=12 March 2022 |work=Robert Koch Institute |archive-date=12 March 2022 |archive-url=https://web.archive.org/web/20220312225756/https://www.rki.de/DE/Content/InfAZ/N/Neuartiges_Coronavirus/Situationsberichte/Wochenbericht/Wochenbericht_2022-03-10.pdf |url-status=live }}</ref><ref name="BBC 11March2022">{{Cite news |author=<!--not stated--> |date=11 March 2022 |title=Covid infections rising again across UK - ONS |work=BBC News |url=https://www.bbc.co.uk/news/health-60709712 |access-date=12 March 2022 |archive-date=13 March 2022 |archive-url=https://web.archive.org/web/20220313191916/https://www.bbc.co.uk/news/health-60709712 |url-status=live }}</ref> In March, BA.1.1 was still heavily dominant in the United States (having overtaken BA.1 in January), but BA.2 was increasing in frequency, later becoming dominant in the US by 29 March.<ref name="CDC Variants" /><ref>{{Cite web |agency=Reuters |title=BA.2 version of omicron is now dominant coronavirus variant in U.S., CDC says |url=https://www.nbcnews.com/health/health-news/omicron-subvariant-ba2-dominant-coronavirus-strain-cdc-rcna21993 |access-date=30 March 2022 |website=NBC News |date=29 March 2022 |archive-date=29 March 2022 |archive-url=https://web.archive.org/web/20220329152148/https://www.nbcnews.com/health/health-news/omicron-subvariant-ba2-dominant-coronavirus-strain-cdc-rcna21993 |url-status=live }}</ref>

==== XE ====
A new BA.1–BA.2 recombinant was isolated in the UK in January 2022, dubbed the "XE" recombinant. It was found by the WHO to be potentially 10% more transmissible than BA.2, making it about 43% to 76% to more transmissible than BA.1, and making the XE recombinant the most contagious variant identified at the time.<ref>{{cite journal |vauthors=Mohapatra RK, Kandi V, Tuli HS, Chakraborty C, Dhama K |date=August 2022 |title=The recombinant variants of SARS-CoV-2: Concerns continues amid COVID-19 pandemic |journal=Journal of Medical Virology |volume=94 |issue=8 |pages=3506–3508 |doi=10.1002/jmv.27780 |pmc=9088633 |pmid=35419806}}</ref>

==== {{anchor|BA.2.12|BA.2.12.1}}BA.2.12 ====
There were two new BA.2 subvariants detected in the US state of [[New York (state)|New York]], which are BA.2.12 (or B.1.1.529.2.12) and BA.2.12.1 (or B.1.1.529.2.12.1), both of which have a significant growth advantage of 23–27% over BA.2 and contributing to a rise in infections in central New York, centred on [[Syracuse, New York|Syracuse]] and [[Lake Ontario]], which later became dominant by 24 May 2022, in the US.<ref>{{cite journal | vauthors = Del Rio C, Malani PN | title = COVID-19 in 2022-The Beginning of the End or the End of the Beginning? | journal = JAMA | volume = 327 | issue = 24 | pages = 2389–2390 | date = June 2022 | pmid = 35622357 | doi = 10.1001/jama.2022.9655 | s2cid = 249096741 | doi-access = free | title-link = doi }}</ref>

==== {{anchor|BA.2.75|BA.2.75.2}}BA.2.75 and BA.2.75.2 ====
The subvariant BA.2.75 (or B.1.1.529.2.75, nicknamed ''Centaurus'' by the media<ref>{{Cite web |last=Evon |first=Dan |name-list-style=vanc |date=14 July 2022 |title=Why Are People Calling COVID-19 Variant BA.2.75 'Centaurus'? |url=https://www.snopes.com/news/2022/07/14/centaurus-covid-19-strain/ |access-date=15 July 2022 |website=Snopes.com |archive-date=18 July 2022 |archive-url=https://web.archive.org/web/20220718220715/https://www.snopes.com/news/2022/07/14/centaurus-covid-19-strain/ |url-status=live }}</ref>), first detected in [[India]] in May 2022, was classified as variant under monitoring by the WHO.<ref>{{Cite web |title=Tracking SARS-CoV-2 variants |url=https://www.who.int/activities/tracking-SARS-CoV-2-variants |access-date=15 July 2022 |website=[[World Health Organization]] (WHO) |archive-date=9 June 2021 |archive-url=https://web.archive.org/web/20210609115218/https://www.who.int/en/activities/tracking-SARS-CoV-2-variants/ |url-status=live }}</ref> Additional newer mutations in this line (like BA.2.75.2 aka B.1.1.529.2.75.2 or ''Chiron'') may be capable of escaping neutralizing antibodies.<ref>{{Cite journal | vauthors = Sheward DJ, Kim C, Fischbach J, Sato K, Muschiol S, Ehling RA, Björkström NK, Karlsson Hedestam GB, Reddy ST, Albert J, Peacock TP, Murrell B |date = November 2022 |title=Omicron sublineage BA.2.75.2 exhibits extensive escape from neutralising antibodies |journal=The Lancet Infectious Diseases |volume=22 |issue=11 |pages=1538–1540 |doi=10.1016/S1473-3099(22)00663-6|pmid=36244347 |pmc=9560757 }}</ref>

===== {{anchor|XBB|XBB.1|XBB.1.5|XBB.1.16|XBB.2|XBB.3}}XBB and XBB.1 =====
XBB, a recombinant of the BA.2.10.1.1 and BA.2.75.3.1.1.1 sublineages,<ref>{{cite web |website=[[World Health Organization]] (WHO) |url=https://www.who.int/activities/tracking-SARS-CoV-2-variants/ |title=Tracking SARS-CoV-2 variants |access-date=22 August 2023 |archive-date=3 February 2023 |archive-url=https://web.archive.org/web/20230203073838/https://www.who.int/activities/tracking-SARS-CoV-2-variants |url-status=live }}</ref> is an Omicron subvariant first detected in August 2022.<ref>{{cite web |url=https://www.channelnewsasia.com/singapore/covid-19-xbb-variant-omicron-bivalent-vaccines-protect-cna-explains-3004006 |work=channelnewsasia.com |date=12 October 2022 |first=Firdaus |last=Hamzah |name-list-style=vanc |title=CNA Explains: What you need to know about the XBB COVID-19 variant |access-date=13 October 2022 |archive-date=8 December 2022 |archive-url=https://web.archive.org/web/20221208095441/https://www.channelnewsasia.com/singapore/covid-19-xbb-variant-omicron-bivalent-vaccines-protect-cna-explains-3004006 |url-status=live }}</ref>

On 20 October 2022, the chief scientist of the World Health Organization (WHO), Soumya Swaminathan, warned that the XBB subvariant of Omicron may cause infections in some countries while the severity of the new variants is not yet known.<ref>{{Cite web |title=Omicron Variant May Cause Another Covid Wave: WHO Chief Scientist |url=https://www.ndtv.com/india-news/omicron-variant-may-cause-another-covid-wave-who-chief-scientist-3450835 |access-date=21 October 2022 |website=NDTV.com |archive-date=9 February 2023 |archive-url=https://web.archive.org/web/20230209151734/https://www.ndtv.com/india-news/omicron-variant-may-cause-another-covid-wave-who-chief-scientist-3450835 |url-status=live }}</ref>

On 9 January 2023 the [[European CDC]] said there was suggestive evidence the XBB.1.5 variant had a growth advantage; after becoming dominant in the US, it might become dominant in Europe in the following months.<ref>{{cite web |publisher=European CDC |date=9 January 2023 |title=Update on SARS-CoV-2 variants: ECDC assessment of the XBB.1.5 sub-lineage |url=https://www.ecdc.europa.eu/en/news-events/update-sars-cov-2-variants-ecdc-assessment-xbb15-sub-lineage |access-date=12 January 2023 |archive-date=18 March 2023 |archive-url=https://web.archive.org/web/20230318122735/https://www.ecdc.europa.eu/en/news-events/update-sars-cov-2-variants-ecdc-assessment-xbb15-sub-lineage |url-status=live }}</ref> From preliminary evidence, they had assessed the XBB variants had no effect on disease severity and transmissibility.<ref>{{cite web |publisher=European CDC |date=9 January 2023 |title=SARS-CoV-2 variants of concern as of 9 January 2023 |url=https://www.ecdc.europa.eu/en/covid-19/variants-concern |access-date=12 January 2023 |archive-date=16 June 2021 |archive-url=https://web.archive.org/web/20210616103810/https://www.ecdc.europa.eu/en/covid-19/variants-concern |url-status=live }}</ref>

In March 2023, XBB.1.16 first appeared in India and caused a surge of hospitalizations.<ref name="mskcc/SARS2/recomb"/> It was [[Colloquial names of SARS-CoV-2 variants|nicknamed]] Arcturus by [[T. Ryan Gregory]].<ref name="mskcc/SARS2/recomb">{{cite web |last1=Boyce |first1=Lindsay |name-list-style=vanc |title=LibGuides: SARS-CoV-2: SARS-CoV-2 Recombination |url=https://libguides.mskcc.org/SARS2/recombination |website=[[Memorial Sloan Kettering Cancer Center]] |access-date=15 April 2023 |date=12 April 2023 |archive-date=15 June 2023 |archive-url=https://web.archive.org/web/20230615163415/https://libguides.mskcc.org/SARS2/recombination |url-status=live }}</ref><ref name="wapo/23/04/14/arcturus-explained">{{cite news |last1=Bisset |first1=Victoria |name-list-style=vanc |title=What to know about Arcturus, a new coronavirus subvariant the WHO is tracking |url=https://www.washingtonpost.com/health/2023/04/14/covid-variant-arcturus-india-explained/ |access-date=15 April 2023 |newspaper=[[Washington Post]] |date=14 April 2023 |archive-date=2 May 2023 |archive-url=https://web.archive.org/web/20230502211357/https://www.washingtonpost.com/health/2023/04/14/covid-variant-arcturus-india-explained/ |url-status=live }}</ref><ref name="webmd/covid-itchy-eyes">{{cite web |last1=O'Mary |first1=Lisa |name-list-style=vanc |title=New COVID Variant on WHO's Radar Causing Itchy Eyes in Kids |url=https://www.webmd.com/covid/news/20230411/new-covid-variant-who-radar-itchy-eyes-kids |website=[[WebMD]] |access-date=16 April 2023 |date=11 April 2023 |archive-date=10 May 2023 |archive-url=https://web.archive.org/web/20230510200415/https://www.webmd.com/covid/news/20230411/new-covid-variant-who-radar-itchy-eyes-kids |url-status=live }}</ref>

===== {{anchor|XBB.1.9.2|EG.5|EG.5.1}} EG.5 and EG.5.1 =====
EG.5 (or XBB.1.9.2.5), nicknamed by some media "Eris",<ref>{{Cite web |last=Johnson |first=Arianna |name-list-style=vanc |title=What We Know About 'Eris' Covid Variant EG.5: The Dominant Strain Driving An Uptick In Cases |url=https://www.forbes.com/sites/ariannajohnson/2023/08/10/what-we-know-about-eris-covid-variant-eg5-the-dominant-stain-driving-an-uptick-in-cases/ |access-date=11 August 2023 |website=Forbes |archive-date=23 August 2023 |archive-url=https://web.archive.org/web/20230823032627/https://www.forbes.com/sites/ariannajohnson/2023/08/10/what-we-know-about-eris-covid-variant-eg5-the-dominant-stain-driving-an-uptick-in-cases/ |url-status=live }}</ref> is a descendant of XBB.1.9.2. The lineage was detected as early as February 2023.<ref>{{Cite web |title=cov-lineages.org |url=https://cov-lineages.org/lineage_list.html |access-date=11 August 2023 |archive-date=27 March 2022 |archive-url=https://web.archive.org/web/20220327093523/https://cov-lineages.org/lineage_list.html |url-status=live }}</ref> On 6 August, the [[UK Health Security Agency]] reported the EG.5 strain was responsible for one in seven new cases in the UK during the third week of July.<ref>{{cite web |first=Smitha |last=Mundasad |name-list-style=vanc |url=https://www.bbc.co.uk/news/health-66461727 |title=What we know about the Covid variant EG.5 dubbed 'Eris' |work=BBC News |publisher=BBC |date=10 August 2023 |access-date=10 August 2023 |archive-date=18 September 2023 |archive-url=https://web.archive.org/web/20230918130247/https://www.bbc.co.uk/news/health-66461727 |url-status=live }}</ref> It was identified as a "variant of interest" by the WHO on 9 August 2023. Its key difference from other strains is a "F456L amino acid mutation".<ref>{{Cite web |date=9 August 2023 |title=EG.5 Initial Risk Evaluation, 9 August 2023 |url=https://www.who.int/docs/default-source/coronaviruse/09082023eg.5_ire_final.pdf?sfvrsn=2aa2daee_1 |access-date=11 August 2023 |website=World Health Organization |archive-date=7 December 2023 |archive-url=https://web.archive.org/web/20231207101452/https://www.who.int/docs/default-source/coronaviruse/09082023eg.5_ire_final.pdf?sfvrsn=2aa2daee_1 |url-status=live }}</ref>

====HV.1====
HV.1 (or XBB.1.9.2.5.1.6.1) is a sublineage of XBB.1.9.2, of the Omicron family first detected in July 2023.

HV.1 overtook EG.5 as the dominant subvariant in the US in October 2023.<ref>{{cite web | url=https://covid.cdc.gov/covid-data-tracker/#variant-proportions | title=COVID Data Tracker | date=28 March 2020 | access-date=12 March 2022 | archive-date=24 August 2020 | archive-url=https://web.archive.org/web/20200824224244/https://covid.cdc.gov/covid-data-tracker/#variant-proportions | url-status=live }}</ref> In October experts stated that there was no evidence that HV.1 was more severe or transmissible than other Omicron subvariants.<ref>{{cite web | last=Fiore | first=Kristina | name-list-style=vanc | title=What to Know About the HV.1 Variant | website=MedPage Today | date=18 October 2023 | url=https://www.medpagetoday.com/special-reports/exclusives/106885 | archive-url=http://web.archive.org/web/20240221172046/https://www.medpagetoday.com/special-reports/exclusives/106885 | archive-date=21 February 2024 | url-status=live | access-date=4 September 2024}}</ref>

==== BA.2.86 ====
{{Excerpt|BA.2.86|only=paragraph}}

=== {{anchor|SV-BA.4|SV-BA.5|BA.4|BA.4.6|BA.5}} BA.4 and BA.5 ===
In April 2022, the WHO announced it was tracking the BA.4 and BA.5 subvariants with BA.4 having been detected in South Africa, Botswana, Denmark, Scotland and England.<ref>{{cite web|title=WHO monitoring 2 more Omicron sub-variants known as BA.4 and BA.5|url=https://www.cbc.ca/news/health/who-monitoring-omicron-sub-variants-1.6415875|publisher=[[Canadian Broadcasting Corporation]]|date=11 April 2022|access-date=13 April 2022|archive-date=13 April 2022|archive-url=https://web.archive.org/web/20220413033018/https://www.cbc.ca/news/health/who-monitoring-omicron-sub-variants-1.6415875|url-status=live}}</ref> Early indications from data collected in South Africa suggested BA.4 and BA.5 have a significant growth advantage over BA.2, which by 12 May earned the status Variant of Concern by the European Centre for Disease Prevention and Control, and, by 20 May, by the [[UK Health Security Agency]].<ref>{{Cite tweet |user=Tuliodna |number=1513529930046648326 |title=New Omicron BA.4 & BA.5 detected in South Africa, Botswana, Belgium, Germany, Denmark, and U.K. Early indications that these new sublineages are increasing as a share of genomically confirmed cases in SA}}</ref><ref>{{Cite web |date=13 May 2022 |title=BREAKING: ECDC upgrades Omicron Sublineages BA.4 and BA. 5 to Variants of Concern from Variants of Interest, making it the first public health authority |url=https://medriva.com/breaking-the-ecdc-has-upgraded-omicron-sub-lineages-ba-4-and-ba-5-to-variants-of-concern-from-variants-of-interest-making-it-the-first-public-health-authority-to-do-so/ |access-date=13 May 2022 |website=Medriva |archive-date=14 May 2022 |archive-url=https://web.archive.org/web/20220514033634/https://medriva.com/breaking-the-ecdc-has-upgraded-omicron-sub-lineages-ba-4-and-ba-5-to-variants-of-concern-from-variants-of-interest-making-it-the-first-public-health-authority-to-do-so/ |url-status=live }}</ref><ref>{{Cite web |title=Ireland and Europe at risk of new Covid surge as two new variants of concern declared |url=https://www.independent.ie/irish-news/health/ireland-and-europe-at-risk-of-new-covid-surge-as-two-new-variants-of-concern-declared/41648115.html |first=Eilish |last=O'Regan |name-list-style=vanc |access-date=13 May 2022 |website=independent |date=13 May 2022 |archive-date=22 August 2023 |archive-url=https://web.archive.org/web/20230822143619/https://www.independent.ie/irish-news/health/ireland-and-europe-at-risk-of-new-covid-surge-as-two-new-variants-of-concern-declared/41648115.html |url-status=live }}</ref><ref>{{Cite web |date=20 May 2022 |title=Two types of Omicron classified as Covid variants of concern in UK |url=https://www.theguardian.com/world/2022/may/20/two-types-omicron-classified-covid-variants-concern-uk-ba4-ba5 |first=Nicola |last=Davis |name-list-style=vanc |access-date=14 June 2022 |website=the Guardian |archive-date=10 June 2022 |archive-url=https://web.archive.org/web/20220610132349/https://www.theguardian.com/world/2022/may/20/two-types-omicron-classified-covid-variants-concern-uk-ba4-ba5 |url-status=live }}</ref> BA.5 was dominant in [[Portugal]] by 25 May, accounting for two-thirds of all new cases there.<ref>{{Cite web |date=25 May 2022 |title=Variant BA.5: après le Portugal, les autres pays européens |url=https://www.sciencesetavenir.fr/sante/variant-ba-5-apres-le-portugal-les-autres-pays-europeens-vont-connaitre-leur-sixieme-vague_163686 |access-date=25 May 2022 |website=Sciences et Avenir |language=fr |archive-date=26 May 2022 |archive-url=https://web.archive.org/web/20220526150226/https://www.sciencesetavenir.fr/sante/variant-ba-5-apres-le-portugal-les-autres-pays-europeens-vont-connaitre-leur-sixieme-vague_163686 |url-status=live }}</ref> By 24 June, BA.4 and BA.5 together had become dominant variants in the UK and Germany.<ref>{{Cite web |last=Gilchrist |first=Karen |name-list-style=vanc |date=24 June 2022 |title=UK Covid cases surge following Queen's Jubilee celebrations, new variants become dominant |url=https://www.cnbc.com/2022/06/24/uk-covid-cases-surge-following-jubilee-bapoint4-bapoint5-become-dominant.html |access-date=24 June 2022 |website=CNBC |archive-date=28 June 2022 |archive-url=https://web.archive.org/web/20220628222903/https://www.cnbc.com/2022/06/24/uk-covid-cases-surge-following-jubilee-bapoint4-bapoint5-become-dominant.html |url-status=live }}</ref><ref>{{Cite web |title=Omikron-Subtyp BA.5 herrscht jetzt in Deutschland vor |url=https://www.saechsische.de/coronavirus/omikron-subtyp-ba-5-herrscht-jetzt-in-deutschland-vor-5713349.html |access-date=24 June 2022 |website=www.saechsische.de |date=24 June 2022 |language=de |archive-date=24 June 2022 |archive-url=https://web.archive.org/web/20220624064621/https://www.saechsische.de/coronavirus/omikron-subtyp-ba-5-herrscht-jetzt-in-deutschland-vor-5713349.html |url-status=live }}</ref><ref>{{Cite web |title=RKI - Coronavirus SARS-CoV-2 - Wochenbericht vom 23.6.2022 |url=https://www.rki.de/DE/Content/InfAZ/N/Neuartiges_Coronavirus/Situationsberichte/Wochenbericht/Wochenbericht_2022-06-23.pdf?__blob=publicationFile |access-date=25 June 2022 |website=www.rki.de |archive-date=23 June 2022 |archive-url=https://web.archive.org/web/20220623195833/https://www.rki.de/DE/Content/InfAZ/N/Neuartiges_Coronavirus/Situationsberichte/Wochenbericht/Wochenbericht_2022-06-23.pdf?__blob=publicationFile |url-status=live }}</ref><ref>{{Cite web |title=BA.5 becomes dominant COVID-19 variant in Germany |url=https://www.thestar.com.my/news/world/2022/06/25/ba5-becomes-dominant-covid-19-variant-in-germany |access-date=25 June 2022 |website=The Star |archive-date=24 June 2022 |archive-url=https://web.archive.org/web/20220624213903/https://www.thestar.com.my/news/world/2022/06/25/ba5-becomes-dominant-covid-19-variant-in-germany |url-status=live }}</ref> These two subvariants became dominant in the United States by 28 June.<ref>{{Cite news |date=28 June 2022 |title=Omicron sub-variants BA.4, BA.5 make up more than 50% of U.S. COVID cases - CDC |work=Reuters |url=https://www.reuters.com/business/healthcare-pharmaceuticals/omicron-sub-variants-ba4-ba5-make-up-more-than-50-us-covid-cases-cdc-2022-06-28/ |access-date=28 June 2022 |archive-date=28 June 2022 |archive-url=https://web.archive.org/web/20220628211651/https://www.reuters.com/business/healthcare-pharmaceuticals/omicron-sub-variants-ba4-ba5-make-up-more-than-50-us-covid-cases-cdc-2022-06-28/ |url-status=live }}</ref><ref>{{Cite news |last=Hassan |first=Adeel |name-list-style=vanc |date=28 June 2022 |title=The Omicron subvariants BA.4 and BA.5 have together become dominant in the U.S., the C.D.C. estimates. |work=The New York Times |url=https://www.nytimes.com/2022/06/28/health/covid-subvariants-ba4-ba5.html |access-date=28 June 2022 |issn=0362-4331 |archive-date=29 June 2022 |archive-url=https://web.archive.org/web/20220629064617/https://www.nytimes.com/2022/06/28/health/covid-subvariants-ba4-ba5.html |url-status=live }}</ref> By June, BA.5 became the dominant subvariant in [[France]], with 59% of new cases linked to it.<ref>{{Cite web |last=SPF |title=COVID-19: point épidémiologique du 30 juin 2022 |url=https://www.santepubliquefrance.fr/maladies-et-traumatismes/maladies-et-infections-respiratoires/infection-a-coronavirus/documents/bulletin-national/covid-19-point-epidemiologique-du-30-juin-2022 |access-date=1 July 2022 |website=www.santepubliquefrance.fr |language=fr |archive-date=10 July 2022 |archive-url=https://web.archive.org/web/20220710153847/https://www.santepubliquefrance.fr/maladies-et-traumatismes/maladies-et-infections-respiratoires/infection-a-coronavirus/documents/bulletin-national/covid-19-point-epidemiologique-du-30-juin-2022 |url-status=live }}</ref><ref>{{Cite web |title=Variant Covid BA.5: majoritaire en France, quels symptômes? |url=https://sante.journaldesfemmes.fr/fiches-maladies/2822907-nouveau-variant-covid-ba5-symptomes-contagion-france/ |access-date=1 July 2022 |website=sante.journaldesfemmes.fr |language=fr |archive-date=9 July 2022 |archive-url=https://web.archive.org/web/20220709095649/https://sante.journaldesfemmes.fr/fiches-maladies/2822907-nouveau-variant-covid-ba5-symptomes-contagion-france/ |url-status=live }}</ref>

In May 2022, a case of a new subvariant BA.5.2.1 was reported in California.<ref>{{Cite web |title=BA.5.2.1 Lineage Report |url=https://outbreak.info/situation-reports?pango=BA.5.2.1 |access-date=29 July 2022 |website=Outbreak.info |archive-date=13 July 2022 |archive-url=https://web.archive.org/web/20220713221712/https://outbreak.info/situation-reports?pango=BA.5.2.1 |url-status=live }}</ref> On 10 July, the city of Shanghai reported its first case of BA.5.2.1, in a man who had flown in from Uganda, sparking a new wave of testing.<ref>{{Cite news |title=Shanghai identifies new COVID Omicron subvariant |url=https://www.reuters.com/world/china/chinas-shanghai-says-new-omicron-subvariant-found-2022-07-10/ |access-date=29 July 2022 |website=Reuters |date=10 July 2022 |archive-date=30 July 2022 |archive-url=https://web.archive.org/web/20220730000631/https://www.reuters.com/world/china/chinas-shanghai-says-new-omicron-subvariant-found-2022-07-10/ |url-status=live }}</ref> On 22 July, the province of Ontario, Canada announced that subvariant BA.5.2.1 overtook BA.2.12.1 as the main variant in circulation in Ontario around 2 July.<ref>{{Cite web |title=SARS-CoV-2 Genomic Surveillance in Ontario, July 22, 2022 |url=https://www.publichealthontario.ca/-/media/documents/ncov/epi/covid-19-sars-cov2-whole-genome-sequencing-epi-summary.pdf?sc_lang=en |access-date=29 July 2022 |website=Public Health Ontario |archive-date=19 July 2021 |archive-url=https://web.archive.org/web/20210719091525/https://www.publichealthontario.ca/-/media/documents/ncov/epi/covid-19-sars-cov2-whole-genome-sequencing-epi-summary.pdf?sc_lang=en |url-status=live }}</ref> Regeneron is reporting that BA.5.2.1 is the main variant in Australia, Belgium, Brunei, Greece and Iceland.<ref>{{Cite web |title=Regeneron COVID-19 Dashboard |url=https://covid19dashboard.regeneron.com/?tab=Home&subTab=Europe |access-date=29 July 2022 |website=Regeneron |archive-date=30 July 2022 |archive-url=https://web.archive.org/web/20220730001237/https://covid19dashboard.regeneron.com/?tab=Home&subTab=Europe |url-status=live }}</ref> The government of Canada also reported in June and July, of the travelers arriving by air who test positive for COVID-19, a substantial proportion were BA.5.2.1.<ref>{{Cite web |title=COVID-19: Summary data about travellers, testing and compliance |url=https://www.canada.ca/en/public-health/services/diseases/coronavirus-disease-covid-19/testing-screening-contact-tracing/summary-data-travellers.html |access-date=29 July 2022 |website=Government of Canada |date=14 May 2021 |archive-date=4 August 2022 |archive-url=https://web.archive.org/web/20220804230413/https://www.canada.ca/en/public-health/services/diseases/coronavirus-disease-covid-19/testing-screening-contact-tracing/summary-data-travellers.html |url-status=live }}</ref> BF.7 is a shortened version of the sub-variants full name, which is BA.5.2.1.7. This sub-variant is part of Omicron's BA.5 variant, which had the highest number of reported cases globally, accounting for 76.2% of all cases.<ref>{{cite web | url=https://kpadhne.com/covid-19-variant-bf-7-symptoms-precautions-transmission-rate-and-more-2023/ | title=Covid-19 Variant BF.7 Symptoms, Precautions, Transmission | date=23 December 2022 | access-date=25 December 2022 | archive-date=30 December 2022 | archive-url=https://web.archive.org/web/20221230163453/https://kpadhne.com/covid-19-variant-bf-7-symptoms-precautions-transmission-rate-and-more-2023/ }}</ref>

==== {{anchor|SV-BQ.1|BQ.1|BQ.1.1}}BQ.1 and BQ.1.1 ====
In October 2022, two BA.5 subvariants were found: BQ.1 (or B.1.1.529.5.3.1.1.1.1.1) and BQ.1.1 (or B.1.1.529.5.3.1.1.1.1.1.1).<ref>{{cite web |title=Verbreitet sich rasant: Eine der "besorgniserregendsten Varianten": So gefährlich ist BQ.1.1 |language=de |work=[[FOCUS online (German magazine)|FOCUS online]] |date=20 October 2022 |url=https://www.focus.de/gesundheit/news/eine-der-besorgniserregendsten-varianten-so-gefaehrlich-ist-bq-1-1_id_167000162.html |access-date=31 October 2022 |url-status=live |archive-url=https://web.archive.org/web/20221031111823/https://www.focus.de/gesundheit/news/eine-der-besorgniserregendsten-varianten-so-gefaehrlich-ist-bq-1-1_id_167000162.html |archive-date=31 October 2022}}</ref><ref>{{cite news |author-last=Danner |author-first=Chas |name-list-style=vanc |title=What We Know About the New and Rising COVID Variants |url=https://nymag.com/intelligencer/article/what-to-know-new-covid-variants-bq-1-bq-1-1-xbb-bf-7.html |access-date=1 November 2022 |work=[[Intelligencer (website)|Intelligencer]] |agency=[[nymag.com]] |publisher=[[Vox Media, LLC]] |date=21 October 2022 |url-status=live |archive-url=https://web.archive.org/web/20221101115417/https://nymag.com/intelligencer/article/what-to-know-new-covid-variants-bq-1-bq-1-1-xbb-bf-7.html |archive-date=1 November 2022}}</ref><ref>{{cite web |title=Neue Corona-Subvariante BQ.1.1 - "Höllenhund"-Virusvariante ist in Deutschland angekommen |author-first=Anja |author-last=Braun |name-list-style=vanc |language=de |date=27 October 2022 |work=SWR Wissen |publisher=[[Südwestrundfunk]] |url=https://www.swr.de/wissen/neue-corona-subvariante-bq1-1-hoellenhund-cerberus-in-deutschland-angekommen-100.html |access-date=31 October 2022 |url-status=live |archive-url=https://web.archive.org/web/20221031093004/https://www.swr.de/wissen/neue-corona-subvariante-bq1-1-hoellenhund-cerberus-in-deutschland-angekommen-100.html |archive-date=31 October 2022}}</ref> The variants were originally most prevalent in France.<ref>{{Cite news |date=25 October 2022 |title=A new Omicron variant, BQ.1.1, is spreading throughout France |work=Le Monde.fr |url=https://www.lemonde.fr/en/environment/article/2022/10/25/a-new-omicron-variant-bq-1-1-is-spreading-throughout-france_6001720_114.html |access-date=20 November 2022 |archive-date=3 January 2023 |archive-url=https://web.archive.org/web/20230103150808/https://www.lemonde.fr/en/environment/article/2022/10/25/a-new-omicron-variant-bq-1-1-is-spreading-throughout-france_6001720_114.html |url-status=live }}</ref> As of 17 November 93% of sequences in France were Omicron sub-lineage BA.5 and among the BA.5 sub-lineages, BQ.1.1 continued to rise (32% vs 25% in the prior week).<ref>{{Cite news |last=sante publique france |title=COVID-19: epidemiological update. Weekly report. Week 45. 17 November 2022. |language=fr |url=https://www.santepubliquefrance.fr/en/covid-19-epidemiological-update.-weekly-report.-week-45.-17-november-2022 |access-date=20 November 2022 |archive-date=28 November 2022 |archive-url=https://web.archive.org/web/20221128070733/https://www.santepubliquefrance.fr/en/covid-19-epidemiological-update.-weekly-report.-week-45.-17-november-2022 |url-status=live }}</ref> In November 2022 in the US it was reported the variants were accounting for 44% of new infections. Early laboratory tests found that these subvariants were better at escaping first and booster vaccines than previous variants.<ref>{{cite news| title=BQ.1 and BQ.1.1 Become New Dominant COVID Subvariants| first=Lisa| last=O'Mary |name-list-style=vanc | website=Medscape| date=14 November 2022| url=https://www.medscape.com/viewarticle/983994| access-date=16 November 2022| archive-date=25 November 2022| archive-url=https://web.archive.org/web/20221125100724/https://www.medscape.com/viewarticle/983994| url-status=live}}</ref>

=== Later subvariants ===
<!-- Please go to the "Variants of SARS-CoV-2" to keep this article updated. -->
{{excerpt|Variants of SARS-CoV-2|Sublineages by year|subsections=yes}}

== Transmission ==
[[File:Novel Coronavirus SARS-CoV-2 (Omicron) (52228029552).jpg|thumb|False-color [[Transmission electron microscopy|transmission electron micrograph]] of an Omicron variant coronavirus, shown in pink, replicating within the cytoplasm of an infected [[Vero cell]]]]

=== In humans ===
In January 2022, [[William Schaffner (professor)|William Schaffner]], professor of infectious diseases at Vanderbilt University Medical Center, compared the contagiousness of the Omicron variant to that of the [[measles]].<ref>{{Cite web |date=28 January 2022 |title=Omicron variant of COVID-19 may be the most contagious virus to ever exist |url=https://www.salon.com/2022/01/27/omicron-variant-of-may-be-the-most-contagious-to-ever-exist-scientists-say/ |url-status=live |archive-url=https://web.archive.org/web/20220128194459/https://www.salon.com/2022/01/27/omicron-variant-of-may-be-the-most-contagious-to-ever-exist-scientists-say/ |archive-date=28 January 2022 |access-date=30 January 2022 |website=Salon |vauthors=Rozsa M, Karlis N}}</ref>

On 15 December 2021, Jenny Harries, head of the UK Health Security Agency, told a parliamentary committee that the [[doubling time]] of COVID-19 in most regions of the UK was now less than two days despite the country's high vaccination rate. She said that the Omicron variant of COVID-19 is "probably the most significant threat since the start of the pandemic", and that the number of cases in the next few days would be "quite staggering compared to the rate of growth that we've seen in cases for previous variants".<ref>{{Cite news |date=15 December 2021 |title=LIVE – Covid: 'Staggering' Omicron case numbers expected – top health official |website=BBC News |url=https://www.bbc.co.uk/news/live/uk-59664383 |url-status=live |access-date=15 December 2021 |archive-url=https://web.archive.org/web/20211222015123/https://www.bbc.com/news/live/uk-59664383 |archive-date=22 December 2021}} See entry for 10:05</ref>

A 2021 study suggested that mutations that promote [[breakthrough infection]]s or antibody-resistance "like those in Omicron" could be a new mechanism for [[viral evolution]] success of SARS-CoV-2 and that such may become a dominating mechanism of its evolution.<ref>{{cite journal |vauthors=Wang R, Chen J, Wei GW |title=Mechanisms of SARS-CoV-2 Evolution Revealing Vaccine-Resistant Mutations in Europe and America |journal=The Journal of Physical Chemistry Letters |volume=12 |issue=49 |pages=11850–11857 |date=December 2021 |pmid=34873910 |pmc=8672435 |doi=10.1021/acs.jpclett.1c03380 |url=https://users.math.msu.edu/users/weig/paper/p272.pdf |url-status=live |access-date=27 January 2022 |archive-url=https://web.archive.org/web/20211218184752/https://users.math.msu.edu/users/weig/paper/p272.pdf |archive-date=18 December 2021}}</ref> A [[preprint]] supports such an explanation of Omicron's spread, suggesting that it "primarily can be ascribed to the [[Antigenic escape|immune evasiveness]] rather than an inherent increase in the [[Basic reproduction number|basic transmissibility]]".<ref>{{cite news |date=5 January 2022 |title=Study findings suggest spread of Omicron can be ascribed to immune evasiveness rather than an increase in transmissibility |work=News-Medical.net |url=https://www.news-medical.net/news/20220105/Study-findings-suggest-spread-of-Omicron-can-be-ascribed-to-immune-evasiveness-rather-than-an-increase-in-transmissibility.aspx |url-status=live |access-date=17 January 2022 |archive-url=https://web.archive.org/web/20220121182541/https://www.news-medical.net/news/20220105/Study-findings-suggest-spread-of-Omicron-can-be-ascribed-to-immune-evasiveness-rather-than-an-increase-in-transmissibility.aspx |archive-date=21 January 2022}}</ref><ref>{{Cite medRxiv |vauthors=Lyngse FP, Mortensen LH, Denwood MJ, Christiansen LE, Møller CH, Skov RL, Spiess K, Fomsgaard A, Lassauniere R, Rasmussen M, Stegger M |date=27 December 2021 |title=SARS-CoV-2 Omicron VOC Transmission in Danish Households |medrxiv=10.1101/2021.12.27.21268278v1}}</ref> Studies showed the variant to escape the majority of existing SARS-CoV-2 neutralizing antibodies, including those in sera from vaccinated and convalescent individuals.<ref>{{cite journal |vauthors=Cao Y, Wang J, Jian F, Xiao T, Song W, Yisimayi A, Huang W, Li Q, Wang P, An R, Wang J, Wang Y, Niu X, Yang S, Liang H, Sun H, Li T, Yu Y, Cui Q, Liu S, Yang X, Du S, Zhang Z, Hao X, Shao F, Jin R, Wang X, Xiao J, Wang Y, Xie XS |title=Omicron escapes the majority of existing SARS-CoV-2 neutralizing antibodies |journal=Nature |volume=602 |issue=7898 |pages=657–663 |date=February 2022 |pmid=35016194 |doi=10.1038/d41586-021-03796-6 |pmc=8866119 |s2cid=245455422}}</ref><ref>{{Cite medRxiv |vauthors=Wilhelm A, Widera M, Grikscheit K, Toptan T, Schenk B, Pallas C, Metzler M, Kohmer N, Hoehl S, Helfritz FA, Wolf T |date=8 December 2021 |title=Reduced Neutralization of SARS-CoV-2 Omicron Variant by Vaccine Sera and Monoclonal Antibodies |medrxiv=10.1101/2021.12.07.21267432}}</ref><ref>{{cite journal |vauthors=Liu L, Iketani S, Guo Y, Chan JF, Wang M, Liu L, Luo Y, Chu H, Huang Y, Nair MS, Yu J, Chik KK, Yuen TT, Yoon C, To KK, Chen H, Yin MT, Sobieszczyk ME, Huang Y, Wang HH, Sheng Z, Yuen KY, Ho DD |title=Striking antibody evasion manifested by the Omicron variant of SARS-CoV-2 |journal=Nature |volume=602 |issue=7898 |pages=676–681 |date=February 2022 |pmid=35016198 |doi=10.1038/d41586-021-03826-3 |s2cid=245462866|doi-access = free | title-link = doi }}</ref><ref>{{Cite medRxiv |vauthors=Roessler A, Riepler L, Bante D, von Laer D, Kimpel J |date=11 December 2021 |title=SARS-CoV-2 B.1.1.529 variant (Omicron) evades neutralization by sera from vaccinated and convalescent individuals |medrxiv=10.1101/2021.12.08.21267491}}</ref> Nevertheless, existing vaccines were expected to protect against severe illness, hospitalizations, and deaths due to Omicron<ref>{{cite web |date=20 December 2021 |title=Omicron Variant: What You Need to Know |url=https://www.cdc.gov/coronavirus/2019-ncov/variants/omicron-variant.html |url-status=live |archive-url=https://web.archive.org/web/20220127152019/https://www.cdc.gov/coronavirus/2019-ncov/variants/omicron-variant.html |archive-date=27 January 2022 |access-date=27 January 2022 |website=Centers for Disease Control and Prevention}}</ref> and, on an individual level, the Omicron variant is milder than earlier variants that evolved when the antibody/vaccination share was lower than it was when Omicron emerged.<ref name="NYT">{{Cite web |author=David Leonhardt |date=5 January 2022 |title=Omicron Is Milder |url=https://www.nytimes.com/2022/01/05/briefing/omicron-risk-milder-pandemic.html |url-status=live |archive-url=https://web.archive.org/web/20220106235801/https://www.nytimes.com/2022/01/05/briefing/omicron-risk-milder-pandemic.html |archive-date=6 January 2022 |access-date=7 January 2022 |work=The New York Times |quote=A few weeks ago, many experts and journalists were warning that the initial evidence from South Africa — suggesting that Omicron was milder than other variants — might turn out to be a mirage. It has turned out to be real.}}</ref>

In contrast to other investigated variants, Omicron showed substantial, population-level, evasion of immunity from prior infection as well as a higher ability to evade immunity induced by vaccines.<ref>{{cite journal |vauthors=Mohsin M, Mahmud S |title=Omicron SARS-CoV-2 variant of concern: A review on its transmissibility, immune evasion, reinfection, and severity |journal=Medicine |volume=101 |issue=19 |pages=e29165 |date=May 2022 |pmid=35583528 |doi=10.1097/MD.0000000000029165 |pmc=9276130 |s2cid=248858919}}</ref>{{Dubious-span|Natural immunity|text=Other research found that the spread of Omicron may contribute to significant natural immunity to reinfection.<ref>{{cite journal | vauthors = Bobrovitz N, Ware H, Ma X, Li Z, Hosseini R, Cao C, Selemon A, Whelan M, Premji Z, Issa H, Cheng B, Abu Raddad LJ, Buckeridge DL, Van Kerkhove MD, Piechotta V, Higdon MM, Wilder-Smith A, Bergeri I, Feikin DR, Arora RK, Patel MK, Subissi L |title=Protective effectiveness of previous SARS-CoV-2 infection and hybrid immunity against the omicron variant and severe disease: a systematic review and meta-regression |journal=The Lancet Infectious Diseases |date=May 2023 |volume=23 |issue=5 |pages=556–567 |doi=10.1016/S1473-3099(22)00801-5|pmid=36681084 |pmc=10014083 }}</ref>|date=August 2024}}

=== In non-human animals ===
In February 2022, the first confirmed case infecting a wild animal was confirmed by researchers at [[Pennsylvania State University]] in [[white-tailed deer]] in [[Staten Island]], N.Y.<ref>{{cite news |title=Why Omicron-infected white-tailed deer pose an especially big risk to humans |url=https://fortune.com/2022/02/08/omicron-infected-white-tail-deer-covid/ |work=Fortune |access-date=13 February 2022 |archive-date=13 February 2022 |archive-url=https://web.archive.org/web/20220213194635/https://fortune.com/2022/02/08/omicron-infected-white-tail-deer-covid/ |url-status=live }}</ref>

=== Surfaces ===
Although [[Transmission of COVID-19|transmission]] via [[fomite]]s is rare, preliminary data indicate that the variant lasts for 194 hours on plastic surfaces and 21 hours on skin, compared with just 56 and 7 hours, respectively, for the original strain.<ref>{{cite news |date=24 January 2022 |title=Omicron survives longer on plastic, skin than prior variants; nose swabbing found best for rapid tests |work=Reuters |url=https://www.reuters.com/business/healthcare-pharmaceuticals/omicron-survives-longer-plastic-skin-than-prior-variants-nose-swabbing-found-2022-01-24/ |url-status=live |access-date=28 January 2022 |archive-url=https://web.archive.org/web/20220128103855/https://www.reuters.com/business/healthcare-pharmaceuticals/omicron-survives-longer-plastic-skin-than-prior-variants-nose-swabbing-found-2022-01-24/ |archive-date=28 January 2022}}</ref><ref>{{cite bioRxiv |biorxiv=10.1101/2022.01.18.476607 |title=Differences in environmental stability among SARS-CoV-2 variants of concern: Omicron has higher stability |date=19 January 2022 |vauthors=Hirose R, Itoh Y, Ikegaya H, Miyazaki H, Watanabe N, Yoshida T, Bandou R, Daidoji T, Nakaya T}}</ref>

== Vaccine effectiveness ==
Pfizer-BioNTech (BNT162b2) and Moderna (mRNA-1273) mRNA vaccines provide reduced protection against asymptomatic disease but do reduce the risk of serious illness.<ref>{{cite journal | vauthors = Zhou H, Møhlenberg M, Thakor JC, Tuli HS, Wang P, Assaraf YG, Dhama K, Jiang S |title=Sensitivity to Vaccines, Therapeutic Antibodies, and Viral Entry Inhibitors and Advances To Counter the SARS-CoV-2 Omicron Variant |journal=Clinical Microbiology Reviews |date=September 2022 |volume=35 |issue=3 |pages=e00014–22 |doi=10.1128/cmr.00014-22|pmid=35862736 |pmc=9491202 }}</ref><ref>{{cite press release |date=8 December 2021 |title=Pfizer And BioNTech Provide Update On Omicron Variant |url=https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-provide-update-omicron-variant |location=New York City and Mainz |publisher=Pfizer |access-date=8 December 2021 |archive-date=21 December 2021 |archive-url=https://web.archive.org/web/20211221074359/https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-provide-update-omicron-variant |url-status=live}}</ref><ref name="briefing31">{{cite tech report|type=Briefing|title=SARS-CoV-2 variants of concern and variants under investigation in England, technical briefing 31|id=GOV-10645|institution=Public Health England|date=10 December 2021|url=https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1040076/Technical_Briefing_31.pdf|format=PDF|access-date=10 December 2021|pages=3–5, 20–22|archive-date=18 December 2021|archive-url=https://web.archive.org/web/20211218141733/https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1040076/Technical_Briefing_31.pdf|url-status=live}}</ref> On 22 December 2021, the [[Imperial College COVID-19 Response Team]] reported an about {{Estimate|41|37|45|unit=%|mini=no}} lower risk of a hospitalization requiring a stay of at least 1 night compared to the Delta variant, and that the data suggested that recipients of 2 doses of the [[Pfizer–BioNTech COVID-19 vaccine|Pfizer–BioNTech]], the [[Moderna COVID-19 vaccine|Moderna]] or the [[Oxford–AstraZeneca COVID-19 vaccine|Oxford–AstraZeneca]] vaccine were substantially protected from hospitalization.<ref name="mrc-hospitalization-england-20211222">{{cite tech report|vauthors=Ferguson N, Ghani A, Hinsley W, Volz E|others=WHO Collaborating Centre for Infectious Disease Modelling, MRC Centre for Global Infectious Disease Analysis|title=Hospitalisation risk for Omicron cases in England|number=Report 50|institution=Imperial College London|date=22 December 2021|doi=10.25561/93035|url=https://www.imperial.ac.uk/mrc-global-infectious-disease-analysis/covid-19/report-50-severity-omicron/|archive-url=https://web.archive.org/web/20211223040712/https://www.imperial.ac.uk/media/imperial-college/medicine/mrc-gida/2021-12-22-COVID19-Report-50.pdf|archive-date=23 December 2021|url-status=live}}</ref> In January 2022, results from Israel suggested that a fourth dose is only partially effective against Omicron. Many cases of infection broke through, albeit "a bit less than in the control group", even though trial participants had higher antibody levels after the fourth dose.<ref>{{Cite web |date=18 January 2022 |title=Israeli trial, world's first, finds 4th dose 'not good enough' against Omicron |url=https://www.timesofisrael.com/israeli-trial-worlds-first-finds-4th-dose-not-good-enough-against-omicron/ |access-date=11 April 2022 |website=www.timesofisrael.com |archive-date=30 March 2022 |archive-url=https://web.archive.org/web/20220330014822/https://www.timesofisrael.com/israeli-trial-worlds-first-finds-4th-dose-not-good-enough-against-omicron/ |url-status=live }}</ref> On 23 December 2021, ''[[Nature (journal)|Nature]]'' indicates that, though Omicron likely weakens vaccine protection, reasonable effectiveness against Omicron may be maintained with currently available vaccination and boosting approaches.<ref name="Cele_2021">{{cite journal |vauthors=Cele S, Jackson L, Khoury DS, Khan K, Moyo-Gwete T, Tegally H, San JE, Cromer D, Scheepers C, Amoako DG, Karim F, Bernstein M, Lustig G, Archary D, Smith M, Ganga Y, Jule Z, Reedoy K, Hwa SH, Giandhari J, Blackburn JM, Gosnell BI, Abdool Karim SS, Hanekom W, von Gottberg A, Bhiman JN, Lessells RJ, Moosa MS, Davenport MP, de Oliveira T, Moore PL, Sigal A |date=February 2022 |title=Omicron extensively but incompletely escapes Pfizer BNT162b2 neutralization |journal=Nature |volume=602 |issue=7898 |pages=654–656 |bibcode=2022Natur.602..654C |doi=10.1038/s41586-021-04387-1 |pmc=8866126 |pmid=35016196 |s2cid=245879254 |collaboration=COMMIT-KZN Team}}</ref><ref>{{cite journal |vauthors=Callaway E |date=December 2021 |title=Omicron likely to weaken COVID vaccine protection |journal=Nature |volume=600 |issue=7889 |pages=367–368 |bibcode=2021Natur.600..367C |doi=10.1038/d41586-021-03672-3 |pmid=34880488 |s2cid=245007078|doi-access = free | title-link = doi }}</ref>

In December, studies, some of which using large nationwide datasets from either Israel and Denmark, found that [[Vaccine efficacy|vaccine effectiveness]] of multiple common two-dosed [[COVID-19 vaccine]]s is substantially lower against the Omicron variant than for other common variants including the [[Delta variant]], and that a new (often a third) dose – a [[booster dose]] – is needed and effective, as it substantially reduces deaths from the disease compared to cohorts who received no booster but two doses.<ref>{{cite journal |vauthors=Arbel R, Hammerman A, Sergienko R, Friger M, Peretz A, Netzer D, Yaron S |date=December 2021 |title=BNT162b2 Vaccine Booster and Mortality Due to Covid-19 |journal=The New England Journal of Medicine |volume=385 |issue=26 |pages=2413–2420 |doi=10.1056/NEJMoa2115624 |pmc=8728797 |pmid=34879190}}</ref><ref>{{Cite medRxiv |vauthors=Khoury DS, Steain M, Triccas J, Sigal A, Davenport MP |date=17 December 2021 |title=A meta-analysis of Early Results to predict Vaccine efficacy against Omicron |medrxiv=10.1101/2021.12.13.21267748}}</ref><ref>{{Cite medRxiv |vauthors=Garcia-Beltran WF, St Denis KJ, Hoelzemer A, Lam EC, Nitido AD, Sheehan ML, Berrios C, Ofoman O, Chang CC, Hauser BM, Feldman J, Gregory DJ, Poznansky MC, Schmidt AG, Iafrate AJ, Naranbhai V, Balazs AB |date=December 2021 |title=mRNA-based COVID-19 vaccine boosters induce neutralizing immunity against SARS-CoV-2 Omicron variant |medrxiv=10.1101/2021.12.14.21267755}}</ref><ref>{{Cite medRxiv |vauthors=Doria-Rose NA, Shen X, Schmidt SD, O'Dell S, McDanal C, Feng W, Tong J, Eaton A, Maglinao M, Tang H, Manning KE, Edara VV, Lai L, Ellis M, Moore K, Floyd K, Foster SL, Atmar RL, Lyke KE, Zhou T, Wang L, Zhang Y, Gaudinski MR, Black WP, Gordon I, Guech M, Ledgerwood JE, Misasi JN, Widge A, Roberts PC, Beigel J, Korber B, Pajon R, Mascola JR, Suthar MS, Montefiori DC |date=December 2021 |title=Booster of mRNA-1273 Strengthens SARS-CoV-2 Omicron Neutralization |medrxiv=10.1101/2021.12.15.21267805v2}}</ref><ref>{{Cite medRxiv |vauthors=Hansen CH, Schelde AB, Moustsen-Helms IR, Emborg HD, Krause TG, Mølbak K, Valentiner-Branth P |date=23 December 2021 |title=Vaccine effectiveness against SARS-CoV-2 infection with the Omicron or Delta variants following a two-dose or booster BNT162b2 or mRNA-1273 vaccination series: A Danish cohort study |collaboration=Infectious Disease Preparedness Group at Statens Serum Institute |medrxiv=10.1101/2021.12.20.21267966}}</ref><ref>{{cite journal |vauthors=Bar-On YM, Goldberg Y, Mandel M, Bodenheimer O, Freedman L, Alroy-Preis S, Ash N, Huppert A, Milo R |date=December 2021 |title=Protection against Covid-19 by BNT162b2 Booster across Age Groups |journal=The New England Journal of Medicine |volume=385 |issue=26 |pages=2421–2430 |doi=10.1056/NEJMoa2115926 |pmc=8728796 |pmid=34879188}}</ref>

Vaccines continue to be recommended for Omicron and its subvariants. Professor Paul Morgan, [[Immunology|immunologist]] at [[Cardiff University]] said, "''I think a blunting rather than a complete loss [of immunity] is the most likely outcome. The virus can't possibly lose every single [[epitope]] on its surface, because if it did that spike protein couldn't work any more. So, while some of the antibodies and T cell clones made against earlier versions of the virus, or against the vaccines may not be effective, there will be others, which will remain effective. (...) If half, or two-thirds, or whatever it is, of the immune response is not going to be effective, and you're left with the residual half, then the more boosted that is the better''."<ref>{{cite news |date=29 November 2021 |title=What does appearance of Omicron variant mean for the double-vaccinated? |work=[[The Guardian]] |location=London |url=https://www.theguardian.com/world/2021/nov/28/what-does-appearance-of-omicron-mean-for-the-double-jabbed |url-status=live |access-date=29 November 2021 |archive-url=https://web.archive.org/web/20211129005024/https://www.theguardian.com/world/2021/nov/28/what-does-appearance-of-omicron-mean-for-the-double-jabbed |archive-date=29 November 2021 |vauthors=Geddes L}}</ref> Professor [[Francois Balloux]] of the Genetics Institute at [[University College London]] said, "''From what we have learned so far, we can be fairly confident that – compared with other variants – Omicron tends to be better able to reinfect people who have been previously infected and received some protection against COVID-19. That is pretty clear and was anticipated from the mutational changes we have pinpointed in its protein structure. These make it more difficult for antibodies to neutralise the virus''."<ref>{{cite web | last=McKie | first=Robin | name-list-style=vanc | title=Omicron: what do we know about the new Covid variant? | website=[[The Guardian]] | date=5 December 2021 | url=https://www.theguardian.com/world/2021/dec/05/omicron-what-do-we-know-about-the-new-covid-variant | archive-url=http://web.archive.org/web/20211205130453/https://www.theguardian.com/world/2021/dec/05/omicron-what-do-we-know-about-the-new-covid-variant | archive-date=5 December 2021 | url-status=live | access-date=4 September 2024}}</ref>

A  2024 study published in ''[[JAMA Network Open]]'' found that vaccinated individuals infected with the Omicron or [[SARS-CoV-2 Delta variant|Delta variants]] of [[COVID-19]] did not have a higher overall risk of developing new [[Autoimmune disease|autoimmune diseases]] compared to those who were not infected.<ref>{{Cite journal |last1=Wee |first1=Liang En |last2=Lim |first2=Jue Tao |last3=Tay |first3=An Ting |last4=Chiew |first4=Calvin J. |last5=Ong |first5=Benjamin |last6=Lye |first6=David Chien Boon |last7=Lahiri |first7=Manjari |last8=Tan |first8=Kelvin Bryan |date=2024-08-30 |title=Autoimmune Sequelae After Delta or Omicron Variant SARS-CoV-2 Infection in a Highly Vaccinated Cohort |url=https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2823018 |journal=JAMA Network Open |language=en |volume=7 |issue=8 |pages=e2430983 |doi=10.1001/jamanetworkopen.2024.30983 |issn=2574-3805 |pmc=11364997 |pmid=39212988}}</ref> Researchers noted that these results differ significantly from many earlier studies, which reported an increased long-term risk of various autoimmune conditions following infection with earlier COVID-19 variants.<ref>{{Cite web |title=No increased autoimmune risk after omicron, delta COVID-19 in boosted patients |url=https://www.healio.com/news/rheumatology/20241023/no-increased-autoimmune-risk-after-omicron-delta-covid19-in-boosted-patients |access-date=2024-10-25 |website=www.healio.com |language=en}}</ref> Those studies, however, did not consider the potential protective effects of COVID-19 vaccination, including booster doses.

=== BA.1 and BA.2 ===
A January 2022 study by the [[UK Health Security Agency]] found that vaccines afforded similar levels of protection against symptomatic disease by BA.1 and BA.2, and in both it was considerably higher after two doses and a booster than two doses without booster,<ref>{{cite news |date=27 January 2022 |title=Boosters increase protection against death from Omicron in over-50s to 95% – UKHSA |work=The Guardian |url=https://www.theguardian.com/world/live/2022/jan/27/covid-news-live-johnson-vows-to-fight-on-despite-lockdown-party-outrage-moderna-begins-trial-of-omicron-specific-booster-shot |url-status=live |access-date=27 January 2022 |archive-url=https://web.archive.org/web/20220129200903/https://www.theguardian.com/world/live/2022/jan/27/covid-news-live-johnson-vows-to-fight-on-despite-lockdown-party-outrage-moderna-begins-trial-of-omicron-specific-booster-shot |archive-date=29 January 2022}}</ref><ref>{{cite web |date=27 January 2022 |title=COVID-19 vaccine surveillance report Week 4 |url=https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1050721/Vaccine-surveillance-report-week-4.pdf |url-status=live |archive-url=https://web.archive.org/web/20220127200539/https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1050721/Vaccine-surveillance-report-week-4.pdf |archive-date=27 January 2022 |access-date=27 January 2022 |publisher=[[UK Health Security Agency]]}}</ref> though because of the gradually waning effect of vaccines, further booster vaccination may later be necessary.<ref name="BBC 11March2022" />

=== BA.4 and BA.5 ===
In May 2022, a [[preprint]] indicated Omicron subvariants BA.4 and BA.5 could cause a large share of [[COVID-19#Immunity|COVID-19]] [[Severe acute respiratory syndrome coronavirus 2#Reinfection|reinfections]], beyond the increase of reinfections caused by the Omicron lineage, even for people who [[Immunological memory|were infected]] by Omicron BA.1 due to increases in immune evasion, especially for the unvaccinated. However, the observed escape of BA.4 and BA.5 from immunity by a BA.1 infection is more moderate than of BA.1 against studied prior cases of immunity (such as immunity from specific vaccines).<ref>{{cite news |date=2 May 2022 |title=How soon after catching COVID-19 can you get it again? |work=ABC News |url=https://www.abc.net.au/news/health/2022-05-03/covid-19-reinfection-what-are-the-odds-of-catching-it-twice/101024180 |access-date=24 June 2022 |archive-date=9 July 2022 |archive-url=https://web.archive.org/web/20220709233023/https://www.abc.net.au/news/health/2022-05-03/covid-19-reinfection-what-are-the-odds-of-catching-it-twice/101024180 |url-status=live }}</ref><ref>{{Cite medRxiv |vauthors=Khan K, Karim F, Ganga Y, Bernstein M, Jule Z, Reedoy K, Cele S, Lustig G, Amoako D, Wolter N, Samsunder N |date=1 May 2022 |title=Omicron sub-lineages BA.4/BA.5 escape BA.1 infection elicited neutralizing immunity |medrxiv=10.1101/2022.04.29.22274477}}</ref>

[[Immunity (medical)#Naturally acquired|Immunity]] from an Omicron infection for unvaccinated and previously uninfected was found to be weak "against non-Omicron variants",<ref>{{cite journal |vauthors=Suryawanshi RK, Chen IP, Ma T, Syed AM, Brazer N, Saldhi P, Simoneau CR, Ciling A, Khalid MM, Sreekumar B, Chen PY, Kumar GR, Montano M, Gascon R, Tsou CL, Garcia-Knight MA, Sotomayor-Gonzalez A, Servellita V, Gliwa A, Nguyen J, Silva I, Milbes B, Kojima N, Hess V, Shacreaw M, Lopez L, Brobeck M, Turner F, Soveg FW, George AF, Fang X, Maishan M, Matthay M, Morris MK, Wadford D, Hanson C, Greene WC, Andino R, Spraggon L, Roan NR, Chiu CY, Doudna JA, Ott M |title=Limited cross-variant immunity from SARS-CoV-2 Omicron without vaccination |journal=Nature |pages=351–355 |date=May 2022 |volume=607 |issue=7918 |pmid=35584773 |doi=10.1038/s41586-022-04865-0 |pmc=9279157 |bibcode=2022Natur.607..351S |s2cid=248890159}}</ref> albeit at the time Omicron is, by a large margin, the dominant variant in sequenced human cases.<ref>{{cite web |title=SARS-CoV-2 sequences by variant |url=https://ourworldindata.org/grapher/covid-variants-bar |access-date=30 June 2022 |website=Our World in Data |archive-date=1 May 2022 |archive-url=https://web.archive.org/web/20220501015852/https://ourworldindata.org/grapher/covid-variants-bar |url-status=live }}</ref>

==== BQ.1 and BQ.1.1 ====
Subvariants [[#BQ.1 and BQ.1.1|BQ.1 and BQ.1.1]] were found in 2022, to be better at escaping first and booster vaccines than previous variants, and to have further reduced the effectiveness of monoclonal antibody treatments.<ref>{{cite web |last1=Huang |first1=Pien |name-list-style=vanc |title=How monoclonal antibodies lost the fight with new COVID variants |website=[[NPR]] |url=https://www.npr.org/sections/health-shots/2022/11/20/1137892932/monoclonal-antibodies-covid-treatment |access-date=15 August 2023 |archive-date=15 August 2023 |archive-url=https://web.archive.org/web/20230815033329/https://www.npr.org/sections/health-shots/2022/11/20/1137892932/monoclonal-antibodies-covid-treatment |url-status=live }}</ref>

== Vaccine adjustments ==
{{See also|Universal coronavirus vaccine}}

In June 2022, [[Pfizer]] and [[Moderna]] developed [[bivalent vaccine]]s to protect against the [[SARS-CoV-2|SARS-CoV-2 wild-type]] and the Omicron variant. The bivalent vaccines are well-tolerated and offer immunity to Omicron superior to previous mRNA vaccines.<ref name="pmid36303305">{{cite journal |vauthors=Shin DH, Smith DM, Choi JY |year=2022 |title=SARS-CoV-2 Omicron Variant of Concern: Everything You Wanted to Know about Omicron but Were Afraid to Ask |journal=[[Yonsei Medical Journal]] |volume=63 |issue=11 |pages=977–983 |doi=10.3349/ymj.2022.0383 |pmc=9629902 |pmid=36303305}}</ref> In September 2022, the United States [[Food and Drug Administration]] (FDA) authorized the bivalent vaccines.<ref>{{cite web | title=COVID-19 Vaccine Boosters | publisher=U.S. [[Food and Drug Administration]] (FDA) | date=27 September 2022 | url=https://www.fda.gov/emergency-preparedness-and-response/coronavirus-disease-2019-covid-19/covid-19-bivalent-vaccine-boosters | archive-url=https://web.archive.org/web/20221008030807/https://www.fda.gov/emergency-preparedness-and-response/coronavirus-disease-2019-covid-19/covid-19-bivalent-vaccine-boosters | archive-date=8 October 2022 | access-date=8 October 2022 }}</ref><ref>{{cite web | title=Moderna COVID-19 Vaccines | website=U.S. [[Food and Drug Administration]] (FDA) | date=7 October 2022 | url=https://www.fda.gov/emergency-preparedness-and-response/coronavirus-disease-2019-covid-19/moderna-covid-19-vaccines | archive-url=https://web.archive.org/web/20221007231627/https://www.fda.gov/emergency-preparedness-and-response/coronavirus-disease-2019-covid-19/moderna-covid-19-vaccines | archive-date=7 October 2022 | url-status=live | access-date=8 October 2022 }}</ref><ref>{{cite web | title=Pfizer-BioNTech COVID-19 Vaccines | website=U.S. [[Food and Drug Administration]] (FDA) | date=3 October 2022 | url=https://www.fda.gov/emergency-preparedness-and-response/coronavirus-disease-2019-covid-19/pfizer-biontech-covid-19-vaccines | archive-url=https://web.archive.org/web/20221008040351/https://www.fda.gov/emergency-preparedness-and-response/coronavirus-disease-2019-covid-19/pfizer-biontech-covid-19-vaccines | archive-date=8 October 2022 | url-status=live | access-date=8 October 2022 }}</ref>

In June 2023, the FDA advised manufacturers that the 2023–2024 formulation of the COVID{{nbhyph}}19 vaccines for use in the US be updated to be a monovalent COVID{{nbhyph}}19 vaccine using the XBB.1.5 lineage of the Omicron variant.<ref>{{cite web | title=Updated COVID-19 Vaccines for Use in the United States Beginning in Fall 2023 | website=U.S. [[Food and Drug Administration]] (FDA) | date=15 June 2023 | url=https://www.fda.gov/vaccines-blood-biologics/updated-covid-19-vaccines-use-united-states-beginning-fall-2023 | access-date=16 June 2023 | archive-date=17 June 2023 | archive-url=https://web.archive.org/web/20230617055759/https://www.fda.gov/vaccines-blood-biologics/updated-covid-19-vaccines-use-united-states-beginning-fall-2023 | url-status=live }} {{PD-notice}}</ref><ref>{{cite report | date=16 June 2023 | title=Recommendation for the 2023-2024 Formula of COVID-19 vaccines in the U.S. | publisher=U.S. [[Food and Drug Administration]] (FDA) | format=PDF | url=https://www.fda.gov/media/169591/download | access-date=16 June 2023 | archive-date=16 June 2023 | archive-url=https://web.archive.org/web/20230616235520/https://www.fda.gov/media/169591/download | url-status=live }}</ref> In June 2024, the FDA advised manufacturers that the 2024–2025 formulation of the COVID{{nbhyph}}19 vaccines for use in the US be updated to be a monovalent COVID{{nbhyph}}19 vaccine using the JN.1 lineage.<ref>{{cite web | title=Updated COVID-19 Vaccines for Use in the United States Beginning in Fall 2024 | website=U.S. [[Food and Drug Administration]] (FDA) | date=5 June 2024 | url=https://www.fda.gov/vaccines-blood-biologics/updated-covid-19-vaccines-use-united-states-beginning-fall-2024 | access-date=19 June 2024 | archive-date=18 June 2024 | archive-url=https://web.archive.org/web/20240618225346/https://www.fda.gov/vaccines-blood-biologics/updated-covid-19-vaccines-use-united-states-beginning-fall-2024 | url-status=live }} {{PD-notice}}</ref>

In October 2024, the [[Committee for Medicinal Products for Human Use]] (CHMP) of the [[European Medicines Agency]] (EMA) gave a positive opinion to update the composition of Bimervax, a vaccine targeting the Omicron XBB.1.16 subvariant.<ref>{{cite web | title=Meeting highlights from the Committee for Medicinal Products for Human Use (CHMP) 14-17 October 2024 | website=[[European Medicines Agency]] (EMA) | date=18 October 2024 | url=https://www.ema.europa.eu/en/news/meeting-highlights-committee-medicinal-products-human-use-chmp-14-17-october-2024 | access-date=21 October 2024}} Text was copied from this source which is copyright European Medicines Agency. Reproduction is authorized provided the source is acknowledged.</ref>

== Signs and symptoms ==
{{Main|Symptoms of COVID-19}} [[Ageusia|Loss of taste]] and [[anosmia|smell]] seem to be uncommon compared to other strains.<ref name="nbcchicago2723960">{{cite news |title=Omicron Symptoms: Here's How They Differ From Other Variants |url=https://www.nbcchicago.com/news/local/omicron-symptoms-heres-how-they-differ-from-other-variants/2723960/ |date=7 January 2022 |work=NBC Chicago |access-date=30 January 2022 |archive-date=24 January 2022 |archive-url=https://web.archive.org/web/20220124045527/https://www.nbcchicago.com/news/local/omicron-symptoms-heres-how-they-differ-from-other-variants/2723960/ |url-status=live}}</ref><ref name="metro.co.uk15967386">{{cite news |last1=Slater |first1=Jack |name-list-style=vanc |title=Is a change to your taste or smell a sign of Omicron? |url=https://metro.co.uk/2022/01/23/are-loss-of-taste-and-smell-symptoms-of-omicron-15967386/ |work=Metro |date=23 January 2022 |access-date=30 January 2022 |archive-date=26 January 2022 |archive-url=https://web.archive.org/web/20220126130605/https://metro.co.uk/2022/01/23/are-loss-of-taste-and-smell-symptoms-of-omicron-15967386/ |url-status=live}}</ref> A unique reported symptom of the Omicron variant is [[night sweats]],<ref name="Scribner2021" /><ref>{{Cite web |url=https://www.gavi.org/vaccineswork/how-do-symptoms-omicron-differ-previous-covid-19-variants |title=How do the symptoms of Omicron differ from previous COVID-19 variants? |website=[[GAVI]] |first=Linda |last=Geddes |name-list-style=vanc |date=17 December 2021 |access-date=13 December 2022 |archive-date=13 December 2022 |archive-url=https://web.archive.org/web/20221213152258/https://www.gavi.org/vaccineswork/how-do-symptoms-omicron-differ-previous-covid-19-variants |url-status=live }}</ref> particularly with the BA.5 subvariant.<ref>{{Cite web |url=https://www.newstalk.com/news/luke-oneill-one-extra-symptom-now-a-sign-of-ba-5-covid-variant-1361461 |website=[[Newstalk]] |first=Jack |last=Quann |name-list-style=vanc |title=Luke O'Neill: Night sweats now a sign of BA.5 COVID variant |date=7 July 2022 |access-date=10 July 2022 |archive-date=20 July 2022 |archive-url=https://web.archive.org/web/20220720000821/https://www.newstalk.com/news/luke-oneill-one-extra-symptom-now-a-sign-of-ba-5-covid-variant-1361461 |url-status=live }}</ref><ref>{{Cite news |url=https://inews.co.uk/news/science/new-covid-symptoms-night-sweats-omicron-ba-5-signs-hot-flushes-1775043 |title=New Covid symptoms: Night sweats emerge as common sign of Omicron BA.5 with 1 in 10 suffering hot flushes |work=[[i (newspaper)|i]] |first=Tom |last=Bawden |name-list-style=vanc |date=2 August 2022 |access-date=13 December 2022 |archive-date=13 December 2022 |archive-url=https://web.archive.org/web/20221213152256/https://inews.co.uk/news/science/new-covid-symptoms-night-sweats-omicron-ba-5-signs-hot-flushes-1775043 |url-status=live }}</ref> A study performed between 1 and 7 December 2021 by the [[Center for Disease Control]] found that: "The most commonly reported symptoms [were] cough, fatigue, and [[Nasal congestion|congestion]] or runny nose" making it difficult to distinguish from a less damaging variant or another virus.<ref name="cdc20211217">{{cite journal |author=((CDC COVID-19 Response Team)) |title=SARS-CoV-2 B.1.1.529 (Omicron) Variant - United States, December 1-8, 2021 |journal=MMWR. Morbidity and Mortality Weekly Report |volume=70 |issue=50 |pages=1731–1734 |date=December 2021 |pmid=34914670 |pmc=8675659 |doi=10.15585/mmwr.mm7050e1 |url=https://www.cdc.gov/mmwr/volumes/70/wr/mm7050e1.htm |access-date=17 December 2021 |publisher=Center for Disease Control |url-status=live |s2cid=245071514 |archive-url=https://web.archive.org/web/20211220233624/https://www.cdc.gov/mmwr/volumes/70/wr/mm7050e1.htm |archive-date=20 December 2021}}</ref> Research published in London on 25 December 2021 suggested the most frequent symptoms stated by users of the Zoe Covid app were "a runny nose, headaches, fatigue, sneezing and sore throats."<ref name="guardian2021"/>
A British Omicron case-control observational study until March 2022 showed a reduction in odds of [[long COVID]] with the Omicron variant versus the Delta variant of 0·24–0·5 depending on age and time since vaccination.<ref>{{Cite journal | vauthors = Antonelli M, Pujol JC, Spector TD, Ourselin S, Steves CJ |date=June 2022 |title=Risk of long COVID associated with delta versus omicron variants of SARS-CoV-2 |journal=The Lancet |volume=399 |issue=10343 |pages=2263–2264 |doi=10.1016/S0140-6736(22)00941-2 |issn=0140-6736 |pmid=35717982|pmc=9212672 }}</ref>

== Virulence ==
As of 6 January 2022, Omicron multiplied around 70 times faster than the [[Delta variant]] in the [[bronchi]] ([[lung]] airways) but evidence suggested it is less severe than previous variants, especially compared to Delta,<ref name="HMS">{{Cite web |author=Harvard Medical School |date=6 January 2022 |title=Coronavirus Resource Center – Harvard Health |url=https://www.health.harvard.edu/diseases-and-conditions/coronavirus-resource-center |archive-url=https://web.archive.org/web/20220111054542/https://www.health.harvard.edu/diseases-and-conditions/coronavirus-resource-center |archive-date=11 January 2022 |access-date=7 January 2022 |work=Harvard Health Publishing |quote=Lab studies, animal studies, and epidemiological data all indicate that Omicron may cause less severe disease than previous variants.}}</ref><ref name="NYT" /> since it might be less able to penetrate deep lung tissue.<ref name="cidrap">{{Cite web |title=Lung tissue study sheds light on fast Omicron spread |url=https://www.cidrap.umn.edu/news-perspective/2021/12/lung-tissue-study-sheds-light-fast-omicron-spread |url-status=live |archive-url=https://web.archive.org/web/20211216054728/https://www.cidrap.umn.edu/news-perspective/2021/12/lung-tissue-study-sheds-light-fast-omicron-spread |archive-date=16 December 2021 |access-date=25 December 2021 |website=CIDRAP|date=15 December 2021 }}</ref> As of January 2022, in southern California infections were 91 percent less fatal than the delta variant, with 51 percent less risk of hospitalization.<ref>{{Cite medRxiv |vauthors=Lewnard JA, Hong VX, Patel MM, Kahn R, Lipsitch M, Tartof SY |date=11 January 2022 |title=Clinical outcomes among patients infected with Omicron (B.1.1.529) SARS-CoV-2 variant in southern California |medrxiv=10.1101/2022.01.11.22269045}}</ref> However, the estimated difference in the intrinsic risk of hospitalization in England largely decreased to 0–30 percent, when reinfections were excluded.<ref name="imperial50">{{Cite web |title=Some reduction in hospitalisation for Omicron v Delta in England: early analysis |url=https://www.imperial.ac.uk/news/232882/some-reduction-hospitalisation-omicron-delta-england/ |url-status=live |archive-url=https://web.archive.org/web/20220122083412/https://www.imperial.ac.uk/news/232882/some-reduction-hospitalisation-omicron-delta-england/ |archive-date=22 January 2022 |access-date=22 January 2022 |website=Imperial College London|date=22 December 2021 }}</ref>

As of 21 January 2022, the risk of hospitalization was the same in BA.1 and BA.2 based on reviews from Denmark, India, South Africa and the United Kingdom.<ref name="YNews 21Jan2022">{{cite news |date=21 January 2022 |title=Government scientists monitoring new BA.2 variant of Omicron |publisher=Yahoo News |url=https://uk.news.yahoo.com/government-monitoring-new-potentially-more-transmissible-omicron-variant-165522269.html |url-status=live |archive-url=https://web.archive.org/web/20220121225510/https://uk.news.yahoo.com/government-monitoring-new-potentially-more-transmissible-omicron-variant-165522269.html |archive-date=21 January 2022 |vauthors=Parker C |access-date=21 January 2022}}</ref><ref name="WHO edition82" /><ref name="WaPo 25Jan2022" /><ref name="TV2 2Jan2022">{{cite news |date=21 January 2022 |title=Ny Omikron-variant tager over i Danmark – det ved vi om den |language=da |publisher=TV2 |url=https://nyheder.tv2.dk/2022-01-21-ny-omikron-variant-tager-over-i-danmark-det-ved-vi-om-den |url-status=live |archive-url=https://web.archive.org/web/20220122142825/https://nyheder.tv2.dk/2022-01-21-ny-omikron-variant-tager-over-i-danmark-det-ved-vi-om-den |archive-date=22 January 2022 |vauthors=Larsen JA |access-date=21 January 2022}}</ref> Norwegian studies showed that the amount of virus in the upper airways was similar in those infected with BA.1 and BA.2.<ref name="FHI wk2" />

== Diagnosis ==
{{See also|COVID-19 testing}} As of November 2021, the chance of detecting an Omicron case particularly depended on a country's sequencing rate, with South Africa sequencing far more samples than any other country in Africa, but at a considerably lower rate than most Western nations.<ref>{{cite news |date=28 November 2021 |title=South Africa, which found the omicron variant first, leads Africa in coronavirus sequencing |newspaper=Washington Post |url=https://www.washingtonpost.com/world/2021/11/28/coronavirus-genetic-sequence-south-africa-variant-omicron/ |url-status=live |access-date=2 December 2021 |archive-url=https://web.archive.org/web/20211202085440/https://www.washingtonpost.com/world/2021/11/28/coronavirus-genetic-sequence-south-africa-variant-omicron/ |archive-date=2 December 2021 |vauthors=Berger M}}</ref><ref>{{cite web |date=2 December 2021 |title=Sequencing by country |url=https://www.gisaid.org/index.php?id=208 |url-status=live |archive-url=https://web.archive.org/web/20211202035209/https://www.gisaid.org/index.php?id=208 |archive-date=2 December 2021 |access-date=2 December 2021 |publisher=GISAID}}</ref> Sequencing the virus from a sample can take weeks limiting the early availability of data.<ref name="lag">{{Cite news |date=15 December 2021 |title=How big is the risk of Omicron in the UK and how do we know? |newspaper=The Guardian |url=https://www.theguardian.com/world/2021/dec/14/how-big-is-the-risk-of-omicron-in-the-uk-and-how-do-we-know |url-status=live |access-date=15 December 2021 |archive-url=https://web.archive.org/web/20211221004237/https://www.theguardian.com/world/2021/dec/14/how-big-is-the-risk-of-omicron-in-the-uk-and-how-do-we-know |archive-date=21 December 2021 |vauthors=Geddes L}}</ref>

In January 2022 the medicine and therapeutic regulatory agency [[Therapeutic Goods Administration]] (TGA) of the Australian Government had only tested one of their 23 approved [[COVID-19 rapid antigen test]]s (RAT) to verify it detected Omicron.<ref>{{cite web |title=Only one approved rapid test in Australia explicitly states it detects Omicron |url=https://www.theguardian.com/australia-news/2022/jan/28/only-one-approved-rapid-test-in-australia-explicitly-states-it-detects-omicron |website=the Guardian |date=27 January 2022 |access-date=30 January 2022 |archive-date=30 January 2022 |archive-url=https://web.archive.org/web/20220130004810/https://www.theguardian.com/australia-news/2022/jan/28/only-one-approved-rapid-test-in-australia-explicitly-states-it-detects-omicron |url-status=live}}</ref> The TGA later updated their approved list to show that all RATs which detected other variants could detect Omicron infections.<ref>{{cite web |title=Post-market review of antigen and rapid antigen tests |url=https://www.tga.gov.au/products/covid-19/covid-19-tests/post-market-review-antigen-and-rapid-antigen-tests |access-date=15 August 2023 |archive-date=15 August 2023 |archive-url=https://web.archive.org/web/20230815041554/https://www.tga.gov.au/products/covid-19/covid-19-tests/post-market-review-antigen-and-rapid-antigen-tests |url-status=live }}</ref> In June 2022, the German federal Paul-Ehrlich-Institute published their findings, that most RATs detected the Omicron Variant.<ref>{{cite web |title=STATEMENT MANY RAPID TESTS DETECT OMICRON |url=https://www.pei.de/SharedDocs/Downloads/EN/newsroom-en/positions/antigen-test-omicron.pdf?__blob=publicationFile&v=5 |website=PEI |date=17 August 2022 |access-date=16 August 2022 |archive-date=16 August 2022 |archive-url=https://web.archive.org/web/20220816221716/https://www.pei.de/SharedDocs/Downloads/EN/newsroom-en/positions/antigen-test-omicron.pdf?__blob=publicationFile&v=5 |url-status=live }}</ref>

=== PCR testing ===
In December 2021, the US FDA published guidelines on how [[PCR test]]s would be affected by Omicron.<ref>{{cite journal|access-date=16 December 2021 |title=SARS-CoV-2 Viral Mutations: Impact on COVID-19 Tests|journal=FDA|date=16 December 2021|url=https://www.fda.gov/medical-devices/coronavirus-covid-19-and-medical-devices/sars-cov-2-viral-mutations-impact-covid-19-tests|archive-date=21 December 2021 |archive-url=https://web.archive.org/web/20211221014639/https://www.fda.gov/medical-devices/coronavirus-covid-19-and-medical-devices/sars-cov-2-viral-mutations-impact-covid-19-tests|url-status=live}}</ref> Tests that detect multiple gene targets were to continue to identify the testee as positive for COVID-19. S-gene dropout or target failure was proposed as a shorthand way of differentiating Omicron from Delta. besides sequencing and genotyping.<ref name="variants">{{Cite web |title=SARS-CoV-2 variants of concern and variants under investigation in England |url=https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1040076/Technical_Briefing_31.pdf |access-date=10 December 2021|archive-date=18 December 2021|archive-url=https://web.archive.org/web/20211218141733/https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1040076/Technical_Briefing_31.pdf |url-status=live}}</ref>

As of December 2021, Denmark and Norway have regarded cases found by their variant qPCR test, which is relatively fast and checks several genes,<ref name="SSI varQPCR">{{cite web |date=21 December 2021 |title=Variant-PCR-testen (tidl. Delta-PCR-testen) |url=https://covid19.ssi.dk/diagnostik/delta-pcr-testen |url-status=live |archive-url=https://web.archive.org/web/20210207104212/https://covid19.ssi.dk/diagnostik/delta-pcr-testen |archive-date=7 February 2021 |access-date=17 January 2022 |publisher=Statens Serum Institut |language=Danish}}</ref> as sufficient for counting it as Omicron, before full sequencing.<ref name="Norway FI Omicron" /><ref>{{Cite web |title=Status på omikron-varianten (B.1.1.529) pr. 05.12.21 |trans-title=Status of the Omicron variant (B.1.1.529) per 05.12.21 |url=https://www.ssi.dk/aktuelt/nyheder/2021/status-pa-omikron-varianten-b11529-pr-051221 |url-status=live |archive-url=https://web.archive.org/web/20211207005415/https://www.ssi.dk/aktuelt/nyheder/2021/status-pa-omikron-varianten-b11529-pr-051221 |archive-date=7 December 2021 |access-date=18 December 2021 |publisher=[[Statens Serum Institut]] |language=da}}</ref>

==== BA.1 and BA.2 differences ====
As of 7 December 2021 it was known that BA.2, unlike BA.1, lacks the characteristic S-gene target failure (SGTF) causing deletion (Δ69-70), by which many [[qPCR]] tests have been able to rapidly detect a case as an Omicron (or Alpha) variant, from the previously dominant [[SARS-CoV-2 Delta variant|Delta]] variant.<ref name="guardian-sublineage-sgtf">{{cite news |date=7 December 2021 |title=Scientists find 'stealth' version of Omicron that may be harder to track |publisher=www.theguardian.com |url=https://www.theguardian.com/world/2021/dec/07/scientists-find-stealth-version-of-omicron-not-identifiable-with-pcr-test-covid-variant |url-status=live |access-date=7 December 2021 |archive-url=https://web.archive.org/web/20211207163912/https://www.theguardian.com/world/2021/dec/07/scientists-find-stealth-version-of-omicron-not-identifiable-with-pcr-test-covid-variant |archive-date=7 December 2021 |vauthors=Sample I, Walker P}}</ref><ref>{{cite news |date=23 January 2022 |title=Stealth Omicron: What is The Fast Spreading Omicron BA.2 Sub-Variant That Can Escape RT-PCR Test? |publisher=india.com |url=https://www.india.com/health/health-health/stealth-omicron-what-is-the-fast-spreading-omicron-ba-2-sub-variant-that-can-escape-rt-pcr-test-all-that-we-know-so-far-5201383/ |url-status=live |access-date=23 January 2022 |archive-url=https://web.archive.org/web/20220123211405/https://www.india.com/health/health-health/stealth-omicron-what-is-the-fast-spreading-omicron-ba-2-sub-variant-that-can-escape-rt-pcr-test-all-that-we-know-so-far-5201383/ |archive-date=23 January 2022}}</ref> Thus, countries which primarily rely on SGTF for detection may overlook BA.2,<ref name="guardian-sublineage-sgtf" /> and British authorities consider SGTF alone as insufficient for monitoring the spread of Omicron.<ref name="YNews 21Jan2022" /> This has resulted in it having been nicknamed 'Stealth Omicron',<ref name="YNews 21Jan2022" /> but because BA.2 still can be separated from other variants through normal full sequencing, or checks of certain other mutations, the nickname is not quite accurate.<ref name="For 21Jan2022" /><ref name="ABC 26Jan2022">{{cite news |date=26 January 2022 |title=Scientists monitoring new omicron subvariant BA.2 |publisher=ABC News |url=https://abcnews.go.com/Health/scientists-monitoring-omicron-subvariant-ba2/story?id=82472629 |url-status=live |archive-url=https://web.archive.org/web/20220201041550/https://abcnews.go.com/Health/scientists-monitoring-omicron-subvariant-ba2/story?id=82472629 |archive-date=1 February 2022 |vauthors=Rajeshuni, N |access-date=2 February 2022}}</ref> As of January 2022, some countries, such as Denmark and Japan, have been using a variant qPCR which tests for several mutations, including [[L452R]].<ref name="SSI varQPCR" /><ref name="Jpn 14Jan2022" /> It can also distinguish Delta, which has L452R,<ref>{{cite web |date=13 December 2021 |title=Delta Variant Report |url=https://outbreak.info/situation-reports/delta |url-status=live |archive-url=https://web.archive.org/web/20211219212244/https://outbreak.info/situation-reports/delta |archive-date=19 December 2021 |access-date=13 December 2021 |publisher=outbreak.info ([[Scripps Research]])}}</ref> and all Omicron subvariants, which do not have L452R.<ref>{{cite web |date=19 December 2021 |title=BA.1 Lineage Report |url=https://outbreak.info/situation-reports?pango=BA.1 |url-status=live |archive-url=https://web.archive.org/web/20211216193850/https://outbreak.info/situation-reports?pango=BA.1 |archive-date=16 December 2021 |access-date=19 December 2021 |publisher=outbreak.info ([[Scripps Research]])}}</ref><ref name="OBI BA2" /> As Omicron became dominant and the Delta variant became rare in 2022, the SGTF mutation that had made Delta and BA.2 similar in qPCR tests was found to be useful for separating BA.1 and BA.2 from each other.<ref name="NYT 24Feb2022">{{cite news |date=24 February 2022 |title=Is the BA.2 version of Omicron worse? Here's what you need to know |work=[[The New York Times]] |url=https://www.nytimes.com/live/2022/02/24/world/covid-19-tests-cases-vaccine#stealth-omicron-ba2-variant |vauthors=Zimmer C, Lyons, PJ |access-date=12 March 2022 |archive-date=12 March 2022 |archive-url=https://web.archive.org/web/20220312023252/https://www.nytimes.com/live/2022/02/24/world/covid-19-tests-cases-vaccine#stealth-omicron-ba2-variant |url-status=live }}</ref>

== Treatment ==
{{See also|Treatment and management of COVID-19}}
As of 28 November 2021, [[Corticosteroid]]s such as [[dexamethasone]] and [[Anti-IL-6|IL6 receptor blockers]] such as [[tocilizumab]] (Actemra) were known to be effective for managing patients with the earlier strains of severe COVID-19 but the impact on the effectiveness of other treatments was being assessed.<ref name="who-update">{{Cite web|date=28 November 2021|title=Update on Omicron |url=https://www.who.int/news/item/28-11-2021-update-on-omicron|url-status=live|website=World Health Organization|archive-date=30 November 2021|archive-url=https://web.archive.org/web/20211130170020/https://www.who.int/news/item/28-11-2021-update-on-omicron}}</ref><ref>{{cite journal |vauthors=Gordon AC, Mouncey PR, Al-Beidh F, Rowan KM, Nichol AD, Arabi YM, Annane D, Beane A, van Bentum-Puijk W, Berry LR, Bhimani Z, Bonten MJ, Bradbury CA, Brunkhorst FM, Buzgau A, Cheng AC, Detry MA, Duffy EJ, Estcourt LJ, Fitzgerald M, Goossens H, Haniffa R, Higgins AM, Hills TE, Horvat CM, Lamontagne F, Lawler PR, Leavis HL, Linstrum KM, Litton E, Lorenzi E, Marshall JC, Mayr FB, McAuley DF, McGlothlin A, McGuinness SP, McVerry BJ, Montgomery SK, Morpeth SC, Murthy S, Orr K, Parke RL, Parker JC, Patanwala AE, Pettilä V, Rademaker E, Santos MS, Saunders CT, Seymour CW, Shankar-Hari M, Sligl WI, Turgeon AF, Turner AM, van de Veerdonk FL, Zarychanski R, Green C, Lewis RJ, Angus DC, McArthur CJ, Berry S, Webb SA, Derde LP |title=Interleukin-6 Receptor Antagonists in Critically Ill Patients with Covid-19 |journal=The New England Journal of Medicine |volume=384 |issue=16 |pages=1491–1502 |date=April 2021 |pmid=33631065 |pmc=7953461 |doi=10.1056/NEJMoa2100433}}</ref>

Relating to [[Monoclonal antibody|monoclonal antibodies]] (mAbs) treatments, similar testing and research is ongoing. Preclinical data on in vitro pseudotyped virus data demonstrate that some mAbs designed to use highly conserved epitopes retain neutralizing activity against key mutations of Omicron substitutions.<ref>{{cite bioRxiv |vauthors=Cathcart AL, Havenar-Daughton C, Lempp FA, Ma D, Schmid M, Agostini ML, Guarino B, Rosen L, Tucker H, Dillen J, Subramanian S |title=The dual function monoclonal antibodies VIR-7831 and VIR-7832 demonstrate potent in vitro and in vivo activity against SARS-CoV-2 |year=2021 |biorxiv=10.1101/2021.03.09.434607}}</ref>
Similar results are confirmed by cryo-electron microscopy and X-ray data, also providing the structural approach and molecular basis for the evasion of humoral immunity exhibited by Omicron antigenic shift as well as the importance of targeting conserved epitopes for vaccine and therapeutics design. While 7 clinical mAbs or mAb cocktails experienced loss of neutralizing activity of 1-2 orders of magnitude or greater relative to the prototypic virus, the S309 mAb, the parent mAb of [[sotrovimab]], neutralized Omicron with only 2-3-fold reduced potency.<ref>{{cite bioRxiv |vauthors=McCallum M, Czudnochowski N, Rosen LE, Zepeda SK, Bowen JE, Dillen JR, Powell A, Croll T, Nix J, Virgin HW, Corti D |title=Structural basis of SARS-CoV-2 Omicron immune evasion and receptor engagement |year=2021 |biorxiv=10.1101/2021.12.28.474380}}</ref>

As of December 2021, most monoclonal antibodies had lost in vitro neutralizing activity against Omicron, with only 3 out of 29 mAbs examined in another study retaining unaltered potency. Furthermore, a fraction of broadly neutralizing sarbecovirus mAbs neutralized Omicron through recognition of antigenic sites outside the RBM, including [[sotrovimab]] (VIR-7831), S2X259 and S2H97.<ref>{{cite journal |vauthors=Cameroni E, Saliba C, Bowen JE, Rosen LE, Culap K, Pinto D, VanBlargan LA, De Marco A, Zepeda SK, Iulio JD, Zatta F, Kaiser H, Noack J, Farhat N, Czudnochowski N, Havenar-Daughton C, Sprouse KR, Dillen JR, Powell AE, Chen A, Maher C, Yin L, Sun D, Soriaga L, Bassi J, Silacci-Fregni C, Gustafsson C, Franko NM, Logue J, Iqbal NT, Mazzitelli I, Geffner J, Grifantini R, Chu H, Gori A, Riva A, Giannini O, Ceschi A, Ferrari P, Cippà P, Franzetti-Pellanda A, Garzoni C, Halfmann PJ, Kawaoka Y, Hebner C, Purcell LA, Piccoli L, Pizzuto MS, Walls AC, Diamond MS, Telenti A, Virgin HW, Lanzavecchia A, Veesler D, Snell G, Corti D |title=Broadly neutralizing antibodies overcome SARS-CoV-2 Omicron antigenic shift |journal=bioRxiv |date=December 2021 |volume=602 |issue=7898 |pmid=34931194 |pmc=8687478 |doi=10.1038/d41586-021-03825-4 }}</ref> However, sotrovimab was not fully active against the BA.2 Omicron sublineage, and in March 2022 the office of the US [[Office of the Assistant Secretary for Preparedness and Response]] (ASPR) stopped distributing the antibody treatment to states where BA.2 was dominant.<ref>{{Cite web |title=March 25, 2022 {{!}} Important Update {{!}} HHS/ASPR |url=https://aspr.hhs.gov/COVID-19/Therapeutics/updates/Pages/important-update-25March2022.aspx |access-date=6 April 2022 |website=aspr.hhs.gov |archive-date=27 January 2023 |archive-url=https://web.archive.org/web/20230127135453/https://aspr.hhs.gov/COVID-19/Therapeutics/updates/Pages/important-update-25March2022.aspx |url-status=live }}</ref>
February 2022 data suggested Omicron caused significant humoral immune evasion, while neutralizing antibodies targeting the [[sarbecovirus]] conserved region remained most effective.<ref>{{cite journal |vauthors=Cao Y, Wang J, Jian F, Xiao T, Song W, Yisimayi A, Huang W, Li Q, Wang P, An R, Wang J, Wang Y, Niu X, Yang S, Liang H, Sun H, Li T, Yu Y, Cui Q, Liu S, Yang X, Du S, Zhang Z, Hao X, Shao F, Jin R, Wang X, Xiao J, Wang Y, Xie XS |title=Omicron escapes the majority of existing SARS-CoV-2 neutralizing antibodies |journal=Nature |volume=602 |issue=7898 |pages=657–663 |date=February 2022 |pmid=35016194 |pmc=8866119 |doi=10.1038/d41586-021-03796-6 |s2cid=245455422}}</ref>

== Epidemiology ==
On 26 November 2021, the South African [[National Institute for Communicable Diseases]] announced that 30,904 COVID-19-tests (in one day) detected 2,828 new COVID-19 infections (a 9.2% positivity rate).<ref>{{cite web |url=https://www.nicd.ac.za/latest-confirmed-cases-of-covid-19-in-south-africa-26-november-2021/ |title=Latest confirmed cases of COVID-19 in South Africa (26 November 2021) |archive-url=https://web.archive.org/web/20211204114003/https://www.nicd.ac.za/latest-confirmed-cases-of-covid-19-in-south-africa-26-november-2021/ |archive-date=4 December 2021 |work=[[National Institute for Communicable Diseases]] |date=26 November 2021 }}</ref>
One week later, on 3 December 2021, the NICD announced that 65,990 COVID-19 tests had found 16,055 new infections (5.7 times as many as seven days before; positive rate 24.3%) and that 72 percent of them were found in [[Gauteng]].<ref>{{cite web |url=https://www.nicd.ac.za/latest-confirmed-cases-of-covid-19-in-south-africa-3-december-2021/ |title=Latest confirmed cases of COVID-19 in South Africa (3 December 2021) |archive-url=https://web.archive.org/web/20211204004931/https://www.nicd.ac.za/latest-confirmed-cases-of-covid-19-in-south-africa-3-december-2021/ |archive-date=4 December 2021 |work=[[National Institute for Communicable Diseases]] |date=3 December 2021 }}</ref><ref>{{cite web | title=Operations Dashboard for ArcGIS | website=NICD GIS Portal | date=28 July 2021 | url=https://gis.nicd.ac.za/portal/apps/opsdashboard/index.html#/15eb33988f104b73867606c1248578ff | archive-url=http://web.archive.org/web/20210908021150/https://gis.nicd.ac.za/portal/apps/opsdashboard/index.html#/15eb33988f104b73867606c1248578ff | archive-date=8 September 2021 | url-status=unfit | access-date=4 September 2024}}</ref>
This [[Provinces of South Africa|province of South Africa]] is densely populated at about 850 inhabitants per km<sup>2</sup>. Gauteng's capital [[Johannesburg]] is [[Megacity#List of megacities|a megacity]] (about 5.5 million inhabitants in the city itself plus 9.5 million in the urban region).{{citation needed|date=August 2023}}

In November 2021, the transmissibility of the Omicron variant, as compared to the Delta variant or other variants of the COVID-19 virus, was still uncertain.<ref name="who-update"/> Omicron is frequently able to infect previously COVID-19-positive people.<ref name="OmicronReinfection">{{Cite medRxiv |vauthors=Pulliam JR, van Schalkwyk C, Govender N, von Gottberg A, Cohen C, Groome MJ, Dushoff J, Mlisana K, Moultrie H |title=SARS-CoV-2 reinfection trends in South Africa: analysis of routine surveillance data. |date=January 2021 |medrxiv=10.1101/2021.11.11.21266068}}</ref><ref>{{Cite web |date=2 December 2021 |title=Omicron seems to carry higher Covid reinfection risk, says South Africa |url=https://www.theguardian.com/global-development/2021/dec/02/omicron-may-cause-more-covid-reinfections-say-south-african-experts |access-date=3 December 2021 |website=The Guardian |archive-date=3 December 2021 |archive-url=https://web.archive.org/web/20211203192321/https://www.theguardian.com/global-development/2021/dec/02/omicron-may-cause-more-covid-reinfections-say-south-african-experts |url-status=live}}</ref>

It has been estimated the Omicron variant diverged in September or October 2021, based on Omicron genome comparisons.<ref>{{Cite web |title='Patience is crucial': Why we won't know for weeks how dangerous Omicron is |url=https://www.science.org/content/article/patience-crucial-why-we-won-t-know-weeks-how-dangerous-omicron|access-date=30 November 2021|website=www.science.org |archive-date=30 November 2021 |archive-url=https://web.archive.org/web/20211130022659/https://www.science.org/content/article/patience-crucial-why-we-won-t-know-weeks-how-dangerous-omicron |url-status=live}}</ref>
Sequencing data suggests that Omicron had become the dominant variant in South Africa by November 2021, the same month where it had been first identified in the country.<ref>{{Cite web |publisher=[[National Institute for Communicable Diseases]] |work=Network for Genomic Surveillance in South Africa |date=26 November 2021 |title=Proportion and number of clades by epiweek in South Africa, 2021 |url=https://www.nicd.ac.za/wp-content/uploads/2021/11/Update-of-SA-sequencing-data-from-GISAID-26-Nov_Final.pdf#page=8 |url-status=live |access-date=2 December 2021 |archive-date=2 December 2021 |archive-url=https://web.archive.org/web/20211202003648/https://www.nicd.ac.za/wp-content/uploads/2021/11/Update-of-SA-sequencing-data-from-GISAID-26-Nov_Final.pdf#page=8}}</ref><ref name="TG SAfrica 2Dec">{{cite news |date=2 December 2021 |title=Omicron becomes dominant variant in South Africa |newspaper=The Guardian |url=https://www.theguardian.com/world/live/2021/dec/02/coronavirus-news-live-south-africa-sees-exponential-increase-in-covid-cases-dominated-by-omicron-variant?page=with:block-61a8197e8f08988db2bebd49#block-61a8197e8f08988db2bebd49 |url-status=live |access-date=2 December 2021 |archive-url=https://web.archive.org/web/20211202032030/https://www.theguardian.com/world/live/2021/dec/02/coronavirus-news-live-south-africa-sees-exponential-increase-in-covid-cases-dominated-by-omicron-variant?page=with%3Ablock-61a8197e8f08988db2bebd49#block-61a8197e8f08988db2bebd49 |archive-date=2 December 2021}}</ref>

Phylogeny suggests a recent emergence. Data from South Africa suggests that Omicron has a pronounced growth advantage there. However, this may be due to transmissibility or immune escape related, or both."<ref>{{Cite web |title=Risk assessment for SARS-CoV-2 variant: Omicron VOC-21NOV-01 (B.1.1.529): 3 December 2021 |url=https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1038442/3_December-2021-risk-assessment-for-SARS_Omicron_VOC-21NOV-01_B.1.1.529.pdf |url-status=live |access-date=4 December 2021 |website=GOV.UK |archive-date=4 December 2021 |archive-url=https://web.archive.org/web/20211204034223/https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1038442/3_December-2021-risk-assessment-for-SARS_Omicron_VOC-21NOV-01_B.1.1.529.pdf}}</ref> Also the serial interval plays a role in the growth.

Detectable changes in levels of COVID-19 in wastewater samples from South Africa's Gauteng province were seen as early as 17–23 October (week 42).<ref>{{cite web|title=Wastewater-based epidemiology for SARS-CoV-2 in South Africa |url=https://www.nicd.ac.za/wp-content/uploads/2021/10/Wastewater-based-epidemiology-for-SARS-CoV-2-surveillance-in-South-Africa-week-42.pdf|url-status=live|access-date=30 November 2021|publisher=[[National Institute for Communicable Diseases]] |vauthors=McCarthy K, Rachida S, Yousif M, Ndlovu N, Iwu-Jaja C, Howard W, Moonsamy S, Pocock G, Coetzee L, Mans J, Schaefer L, Le Roux WJ, Gomba A, Jambo D, De Villiers DM, Lepart NL, Johnson R, Muller C, Van der Walt M, Mutshembele A, Berkowitz N, Bhagwan J, Suchard M|archive-date=9 November 2021|archive-url=https://web.archive.org/web/20211109222209/https://www.nicd.ac.za/wp-content/uploads/2021/10/Wastewater-based-epidemiology-for-SARS-CoV-2-surveillance-in-South-Africa-week-42.pdf}}</ref> The National Institute for Communicable Diseases reports that children under the age of 2 make up 10% of total hospital admissions in the Omicron point of discovery [[Tshwane]] in South Africa.<ref>{{cite news |title=COVID-19: Toddlers make up 10% of hospital cases in South Africa's Omicron epicentre |url=https://gulfnews.com/world/africa/covid-19-toddlers-make-up-10-of-hospital-cases-in-south-africas-omicron-epicentre-1.84075071 |work=gulfnews.com |access-date=2 December 2021 |archive-date=2 December 2021 |archive-url=https://web.archive.org/web/20211202184133/https://gulfnews.com/world/africa/covid-19-toddlers-make-up-10-of-hospital-cases-in-south-africas-omicron-epicentre-1.84075071 |url-status=live}}</ref> Data on the S gene target failure (SGTF) of sampled cases in South Africa indicates a growth of 21% per day relative to Delta, generating an increased reproduction number by a factor of 2.4.{{efn|With a presumed identical person-to-person serial interval of log<sub>e</sub>(2.4)/0.21 ~ 4.2 days, or a distribution thereof to the same effect.}} Omicron became the majority strain in South Africa around 10 November.<ref>{{Cite web |title=Omicron Spread in South Africa |url=https://drive.google.com/file/d/1hA6Mec2Gq3LGqTEOj35RqSeAb_SmXpbI/view |page=6 |url-status=live |access-date=4 December 2021 |archive-date=4 December 2021 |archive-url=https://web.archive.org/web/20211204113942/https://drive.google.com/file/d/1hA6Mec2Gq3LGqTEOj35RqSeAb_SmXpbI/view}}</ref><ref>{{Cite news |vauthors=Mandavilli A |date=4 December 2021 |title=Omicron Variant Spreading Twice as Quickly as Delta in South Africa |work=The New York Times |url=https://www.nytimes.com/2021/12/03/health/coronavirus-omicron-vaccines-contagiousness.html |access-date=4 December 2021 |issn=0362-4331 |archive-date=4 December 2021 |archive-url=https://web.archive.org/web/20211204113942/https://www.nytimes.com/2021/12/03/health/coronavirus-omicron-vaccines-contagiousness.html |url-status=live}}</ref> Another analysis showed 32% growth per day in Gauteng, South Africa, having become dominant there around 6 November.<ref>{{Citation |title=The SARS-CoV-2 variant Omicron: a snapshot of where we are – 08.12.2021, 5 PM CET. | date=8 December 2021 |url=https://www.youtube.com/watch?v=BMSG8TUObsE |access-date=10 December 2021 |archive-date=21 December 2021 |archive-url=https://web.archive.org/web/20211221005844/https://www.youtube.com/watch?app=desktop&v=BMSG8TUObsE |url-status=live}}</ref>

In the UK, the logarithmic growth rate of Omicron-associated S gene target failure (SGTF) cases over S gene target positive (SGTP) cases was estimated at 0.37 per day,{{efn|Logarithmic growth rate of 0.37/day means that the log odds log<sub>e</sub>(SGTF/SGTP) is increasing by 0.37 in a day. So SGTF/SGTP was increasing by a multiplicative factor of exp(0.37) ~ 1.45. This is substantially higher than a naive increase to 100%+37%. The difference is mathematically due to compound growth within the day, which does not imply that epidemically people are already infectious within a day. Rather, simplified (non-delay) differential equations are used for convenience for the modeling. This also indicates a doubling time of log<sub>e</sub>(2)/(0.37/day) ~ 1. days for the Omicron to Delta prevalence ratio.}} which is exceptionally high.<ref>{{Cite web |title=Prof. Albertsen deliberations |url=https://twitter.com/madsalbertsen85/status/1469331924447600652 |access-date=11 December 2021 |website=Twitter |archive-date=14 December 2021 |archive-url=https://web.archive.org/web/20211214224945/https://twitter.com/MadsAlbertsen85/status/1469331924447600652 |url-status=live}}</ref> Furthermore, by 14 December it appears to have become the most dominant strain.{{efn|Referring to ref 12 in the reference, where the x-axis is crossed at 14 December.}}<ref>{{Cite web |date=23 December 2021 |title=SARS-CoV-2 variants of concern and variants under investigation in England – Technical briefing 33 |url=https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1043807/technical-briefing-33.pdf |url-status=live |archive-date=2 January 2022 |website=gov.uk |publisher=UK Health Security Agency |access-date=15 January 2022 |archive-url=https://web.archive.org/web/20220102053957/https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1043807/technical-briefing-33.pdf}}</ref> Without presuming behavior change in response to the variant, a million infections per day by 24 December are projected for a 2.5 days doubling time.{{efn|A doubling time of 2.5 days corresponds to an exponential growth rate of ln(2)/(2.5 days) ~ 0.28/day. Direct comparison to the logistic growth rate needs to take the growth/decline of Delta into account.}}<ref name="variants"/> In Denmark, the growth rate has been roughly similar with a doubling time of about 2–3 days, it having become the most prevalent strain on 17 December.<ref>{{Cite report |url=https://www.ssi.dk/-/media/cdn/files/covid19/omikron/statusrapport/rapport-omikronvarianten-20122021-9j51.pdf?la=da |title=Covid-19 Rapport om omikronvarianten |date=20 December 2021 |publisher=[[Statens Serum Institut]] |language=Danish |access-date=21 December 2021 |trans-title=Status of the SARS-CoV-2 variant Omicron in Denmark |url-status=live |archive-date=21 December 2021 |archive-url=https://web.archive.org/web/20211221072858/https://www.ssi.dk/-/media/cdn/files/covid19/omikron/statusrapport/rapport-omikronvarianten-20122021-9j51.pdf?la=da}}</ref><ref>{{Cite report |title=Ekspertrapport den 17. december 2021 – Scenarier for smittetal og nyindlæggelser med omikronvarianten |trans-title=Expert report 17 December 2021 – Scenarios for infection numbers and new hospitalizations with the Omicron-variant|url=https://www.ssi.dk/-/media/cdn/files/ekspertrapport-den-17-december-2021.pdf?la=da|url-status=live|publisher=[[Statens Serum Institut]]|date=18 December 2021 |language=Danish |access-date=18 December 2021|archive-date=19 December 2021|archive-url=https://web.archive.org/web/20211219033714/https://www.ssi.dk/-/media/cdn/files/ekspertrapport-den-17-december-2021.pdf?la=da}}</ref><ref>{{Cite web |title=Variant-PCR svar fra 27. nov. og frem, Testcenter Danmark|url=https://files.ssi.dk/covid19/podepind-sekventering/variant-pcr-test-december2021/opgoerelse-variantpcr-covid19-27122021-sp27|url-status=live|language=DA|access-date=27 December 2021 |archive-date=27 December 2021 |archive-url=https://web.archive.org/web/20211227224020/https://files.ssi.dk/covid19/podepind-sekventering/variant-pcr-test-december2021/opgoerelse-variantpcr-covid19-27122021-sp27}}</ref> Switzerland is not far behind.<ref>{{Cite web |title=Schweiz sitrep |url=https://news.in-24.com/news/369062.html |url-status=live|access-date=10 December 2021 |website=Twitter |date=10 December 2021|archive-date=12 December 2021|archive-url=https://web.archive.org/web/20211212192653/https://news.in-24.com/news/369062.html}}</ref> In Germany Omicron became the most prevalent variant on 1 January.<ref>{{Cite web |title=RKI – Coronavirus SARS-CoV-2 – Wochenbericht vom 13.1.2022 |url=https://www.rki.de/DE/Content/InfAZ/N/Neuartiges_Coronavirus/Situationsberichte/Wochenbericht/Wochenbericht_2022-01-13.pdf |access-date=13 January 2022 |website=www.rki.de |archive-date=24 January 2022 |archive-url=https://web.archive.org/web/20220124053801/https://www.rki.de/DE/Content/InfAZ/N/Neuartiges_Coronavirus/Situationsberichte/Wochenbericht/Wochenbericht_2022-01-13.pdf |url-status=live}}</ref> In Scotland, Omicron apparently became the most prevalent variant on 17 December.<ref>{{Cite web |title=Omicron in Scotland – evidence paper|url=http://www.gov.scot/publications/omicron-scotland-evidence-paper/ |access-date=11 December 2021 |website=www.gov.scot |archive-date=20 December 2021 |archive-url=https://web.archive.org/web/20211220035357/https://www.gov.scot/publications/omicron-scotland-evidence-paper/ |url-status=live}}</ref><ref>{{Citation |vauthors=Wenseleers T |title=tomwenseleers/newcovid_belgium |date=22 December 2021 |url=https://github.com/tomwenseleers/newcovid_belgium/blob/8a8ac36c1d166a85e7fac2b7a657cabfa3e1a46e/data/omicron_sgtf/sgtf_scotland.csv |access-date=22 December 2021 |archive-date=22 December 2021 |archive-url=https://web.archive.org/web/20211222215038/https://github.com/tomwenseleers/newcovid_belgium/blob/8a8ac36c1d166a85e7fac2b7a657cabfa3e1a46e/data/omicron_sgtf/sgtf_scotland.csv|url-status=live}}</ref> In the Canadian province of Ontario it became the most prevalent strain on 13 December.<ref>{{Cite web|title=Ontario Dashboard |url=https://covid19-sciencetable.ca/ontario-dashboard/|access-date=12 December 2021 |website=Ontario COVID-19 Science Advisory Table|archive-date=17 March 2021|archive-url=https://web.archive.org/web/20210317110549/https://covid19-sciencetable.ca/ontario-dashboard/ |url-status=live}}</ref> In the US, the variant appears to have become the most prevalent strain on 18 December, growing at 0.24 per day.<ref>{{Cite web |date=28 March 2020|title=COVID Data Tracker |url=https://covid.cdc.gov/covid-data-tracker|access-date=21 December 2021|website=Centers for Disease Control and Prevention |archive-date=22 May 2021|archive-url=https://web.archive.org/web/20210522045354/https://covid.cdc.gov/covid-data-tracker/|url-status=live}}</ref> In Portugal, Omicron had reached 61.5% of cases on 22 December.<ref>{{cite news |title=Portugal says Omicron dominant, infections rising |url=https://www.news9live.com/buzz/coronavirus-live-updates-covid-19-omicron-variant-new-cases-in-india-vaccination-december-25-107888 |date=25 December 2021 |publisher=NewsNine |access-date=28 December 2021 |archive-date=28 December 2021 |archive-url=https://web.archive.org/web/20211228211922/https://www.news9live.com/buzz/coronavirus-live-updates-covid-19-omicron-variant-new-cases-in-india-vaccination-december-25-107888 |url-status=live}}</ref> In Belgium, the strain has become the most prevalent on 25 December,<ref>{{Citation |vauthors=Wenseleers T |title=tomwenseleers/newcovid_belgium |date=20 December 2021 |url=https://github.com/tomwenseleers/newcovid_belgium/blob/main/plots/omicron_sgtf/spread%20omicron%20logistic%20fit%20sgtf%20data.png |access-date=21 December 2021 |archive-date=22 December 2021 |archive-url=https://web.archive.org/web/20211222014420/https://github.com/tomwenseleers/newcovid_belgium/blob/main/plots/omicron_sgtf/spread%20omicron%20logistic%20fit%20sgtf%20data.png |url-status=live}}</ref> and in the Netherlands on 28 December.<ref>{{Cite web |work=[[National Institute for Public Health and the Environment]] |title=Variants of the coronavirus SARS-CoV-2 in the Netherlands |url=https://www.rivm.nl/en/coronavirus-covid-19/virus/variants |url-status=live |access-date=14 January 2022 |archive-date=11 January 2022 |archive-url=https://web.archive.org/web/20220111142337/https://www.rivm.nl/en/coronavirus-covid-19/virus/variants}}</ref> In Italy, it had reached 28% of cases on 20 December and was doubling every two days,<ref>{{cite news |title=COVID: Omicron accountts for 28% of cases in Italy, will soon be dominant |url=https://www.ansa.it/english/news/2021/12/23/covid-omicron-28-of-cases-will-soon-be-dominant_b1bdc895-2640-4f84-a569-7af29eba9061.html |date=23 December 2021 |publisher=ANSA.en |access-date=28 December 2021 |archive-date=24 December 2021 |archive-url=https://web.archive.org/web/20211224151415/https://www.ansa.it/english/news/2021/12/23/covid-omicron-28-of-cases-will-soon-be-dominant_b1bdc895-2640-4f84-a569-7af29eba9061.html |url-status=live}}</ref> while it became the dominant variant in Norway on 25 December.<ref>{{Cite web |vauthors=Oppdatert P |title=Statistikk over meldte tilfeller av virusvarianten omikron|date=8 December 2021 |url=https://www.fhi.no/sv/smittsomme-sykdommer/corona/meldte-tilfeller-av-ny-virusvariant/ |access-date=29 December 2021 |publisher=[[Folkehelseinstituttet]] |language=no |archive-date=28 December 2021 |archive-url=https://web.archive.org/web/20211228150457/https://www.fhi.no/sv/smittsomme-sykdommer/corona/meldte-tilfeller-av-ny-virusvariant/ |url-status=live}}</ref> In France, it made up about 15% of COVID-19 cases in December, but around 27 December it had increased to more than 60%.<ref>{{cite news |title=Covid-19: Omicron is now the dominant variant in France |url=https://www.france24.com/en/europe/20211231-covid-19-omicron-is-now-dominant-variant-in-france |date=31 December 2021 |publisher=France24 |access-date=31 December 2021 |archive-date=3 January 2022 |archive-url=https://web.archive.org/web/20220103133604/https://www.france24.com/en/europe/20211231-covid-19-omicron-is-now-dominant-variant-in-france |url-status=live}}</ref><ref>{{cite news |title=Omicron is now the dominant variant in France |url=https://edition.cnn.com/world/live-news/omicron-variant-coronavirus-news-12-31-21/h_b39ee1ef15221436390eb303e3a95c86 |date=31 December 2021 |publisher=CNN |access-date=31 December 2021 |archive-date=31 December 2021 |archive-url=https://web.archive.org/web/20211231170601/https://edition.cnn.com/world/live-news/omicron-variant-coronavirus-news-12-31-21/h_b39ee1ef15221436390eb303e3a95c86 |url-status=live}}</ref> Researchers recommend sampling at least 5% of COVID-19 patient samples in order to detect Omicron or other emerging variants.<ref>{{cite journal |vauthors=Maxmen A |title=Omicron blindspots: why it's hard to track coronavirus variants |journal=Nature |volume=600 |issue=7890 |page=579 |date=December 2021 |pmid=34916668 |doi=10.1038/d41586-021-03698-7 |s2cid=245262198 |bibcode=2021Natur.600..579M |doi-access = free | title-link = doi }}</ref>

During January 2022, in Denmark the BA.2 variant grew at ~0.10 per day (+11% per day) as a ratio to BA.1 (the legacy Omicron variant), and became the dominant strain in week 2, 2022.<ref name="C19DK" /> In the United Kingdom, the BA.2 variant was growing at ~0.11 per day (+12% per day) as a ratio to BA.1.<ref>{{Cite web |title=SARS-CoV-2 variants of concern and variants under investigation in England, Technical briefing 38 |url=https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1060337/Technical-Briefing-38-11March2022.pdf |access-date=3 January 2022 |work=assets.publishing.service.gov.uk}}</ref>

On 13 January 2022, the [[BBC]] reported that the hospitalization rate was higher in the US and Canada than in Europe and South Africa. This was attributed to a combination of a greater number of elderly people than in South Africa, greater prevalence of comorbidities such as hypertension and obesity than in Europe, higher indoor transmission due to the winter, lower vaccination rate in the US than in Europe and Canada, and a possible still high prevalence of the [[SARS-CoV-2 Delta variant|Delta variant]], which more often leads to hospitalization.<ref>{{cite news |title=The puzzle of America's record Covid hospital rate |url=https://www.bbc.com/news/world-us-canada-59960949 |access-date=14 January 2022 |work=BBC News |date=13 January 2022 |archive-date=14 January 2022 |archive-url=https://web.archive.org/web/20220114051024/https://www.bbc.com/news/world-us-canada-59960949 |url-status=live }}</ref>

=== Reported cases ===
{{SARS-CoV-2 Omicron variant cases}}

== See also ==
<!-- Please keep entries in alphabetical order & add a short description [[WP:SEEALSO]] -->
* [[Timeline of the SARS-CoV-2 Omicron variant]]
* [[Variants of SARS-CoV-2]]
** Other variants of either interest or concern: [[SARS-CoV-2 Alpha variant|Alpha]], [[SARS-CoV-2 Beta variant|Beta]], [[SARS-CoV-2 Gamma variant|Gamma]], [[SARS-CoV-2 Delta variant|Delta]], [[SARS-CoV-2 Epsilon variant|Epsilon]], [[SARS-CoV-2 Zeta variant|Zeta]], [[SARS-CoV-2 Eta variant|Eta]], [[SARS-CoV-2 Theta variant|Theta]], [[SARS-CoV-2 Iota variant|Iota]], [[SARS-CoV-2 Kappa variant|Kappa]], [[SARS-CoV-2 Lambda variant|Lambda]], [[SARS-CoV-2 Mu variant|Mu]]
* [[Sikhulile Moyo]], scientist who discovered SARS-CoV-2 Omicron
<!-- please keep entries in alphabetical order -->

== Notes ==
{{notelist}}

== References ==
{{reflist}}

== External links ==
{{Scholia|disease}}
{{commons category}}
* Archived video:
** {{cite AV media |vauthors=Mohale F, Phaahla J, Oliveira T, Lessels R, Gottberg A, Moore P, Crisp N |date=25 November 2021 |title=Health Department briefs media about a new so-called super-variant |url=https://www.youtube.com/watch?v=b4aTIoZDQk4 |access-date=27 November 2021 |location=South Africa |publisher=[[eNCA]] |via=YouTube |archive-url=https://web.archive.org/web/20211127002250/https://www.youtube.com/watch?v=b4aTIoZDQk4 |archive-date=27 November 2021 |url-status=live }}
** {{cite AV media |people=Oliveira T, Kamwendo S |date=26 November 2021 |title=Professor Tulio de Oliviera on the new COVID-19 variant |url=https://www.youtube.com/watch?v=dMlqRsJ8vuU |archive-url=https://web.archive.org/web/20211126190052/https://www.youtube.com/watch?v=dMlqRsJ8vuU |archive-date=26 November 2021 |access-date=27 November 2021 |publisher=[[SABC News]] |via=YouTube }} Also archived at [https://ghostarchive.org/varchive/dMlqRsJ8vuU Ghostarchive].

{{COVID-19 pandemic}}
{{Portal bar|COVID-19|Medicine|Viruses|Africa}}
{{Authority control}}

[[Category:Variants of SARS-CoV-2|S013]]
[[Category:COVID-19 pandemic in South Africa]]
[[Category:2021 in health]]
[[Category:COVID-19 pandemic in Botswana]]