COVID-19 vaccine

How COVID-19 vaccines work. The video shows the process of vaccination, from injection with RNA or viral vector vaccines, to uptake and translation, and on to immune system stimulation and effect.

Map showing share of population fully vaccinated against COVID-19 relative to a country's total population

Map of countries by approval status

  Approved for general use, mass vaccination underway

  EUA (or equivalent) granted, mass vaccination underway

  EUA granted, limited vaccination

  Approved for general use, mass vaccination planned

  EUA granted, mass vaccination planned

  EUA pending

  No data available

A COVID‑19 vaccine is a vaccine intended to provide acquired immunity against severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2), the virus that causes coronavirus disease 2019 (COVID‑19). Prior to the COVID‑19 pandemic, an established body of knowledge existed about the structure and function of coronaviruses causing diseases like severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). This knowledge accelerated the development of various vaccine platforms during early 2020. The initial focus of SARS-CoV-2 vaccines was on preventing symptomatic, often severe illness. On 10 January 2020, the SARS-CoV-2 genetic sequence data was shared through GISAID, and by 19 March, the global pharmaceutical industry announced a major commitment to address COVID-19. The COVID‑19 vaccines are widely credited for their role in reducing the spread, severity, and death caused by COVID-19.

Many countries have implemented phased distribution plans that prioritize those at highest risk of complications, such as the elderly, and those at high risk of exposure and transmission, such as healthcare workers. Single dose interim use is under consideration to extend vaccination to as many people as possible until vaccine availability improves.

As of 22 September 2021, 6.3 billion doses of COVID‑19 vaccines have been administered worldwide based on official reports from national public health agencies. AstraZeneca anticipates producing 3 billion doses in 2021, Pfizer–BioNTech 1.3 billion doses, and Sputnik V, Sinopharm, Sinovac, and Janssen 1 billion doses each. Moderna targets producing 600 million doses and Convidecia 500 million doses in 2021. By December 2020, more than 10 billion vaccine doses had been preordered by countries, with about half of the doses purchased by high-income countries comprising 14% of the world's population.

Background

A US airman receiving a COVID-19 vaccine, December 2020

Prior to COVID‑19, a vaccine for an infectious disease had never been produced in less than several years – and no vaccine existed for preventing a coronavirus infection in humans. However, vaccines have been produced against several animal diseases caused by coronaviruses, including (as of 2003) infectious bronchitis virus in birds, canine coronavirus, and feline coronavirus. Previous projects to develop vaccines for viruses in the family Coronaviridae that affect humans have been aimed at severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). Vaccines against SARS and MERS have been tested in non-human animals.

According to studies published in 2005 and 2006, the identification and development of novel vaccines and medicines to treat SARS was a priority for governments and public health agencies around the world at that time. There is no cure or protective vaccine proven to be safe and effective against SARS in humans. There is also no proven vaccine against MERS. When MERS became prevalent, it was believed that existing SARS research might provide a useful template for developing vaccines and therapeutics against a MERS-CoV infection. As of March 2020, there was one (DNA-based) MERS vaccine which completed Phase I clinical trials in humans, and three others in progress, all being viral-vectored vaccines: two adenoviral-vectored (ChAdOx1-MERS, BVRS-GamVac) and one MVA-vectored (MVA-MERS-S).

As multiple COVID-19 vaccines have been authorized or licensed for use, real-world vaccine effectiveness (RWE) is now being assessed using case control and observational studies. A study is investigating the long-lasting protection against SARS-CoV-2 provided by the mRNA vaccines. On 10 August 2021, a study showed that the full vaccination coverage rate is correlated inversely to the SARS-CoV-2 delta variant mutation frequency in 16 countries (R-squared=0.878).

Formulation

As of September 2020, eleven of the vaccine candidates in clinical development use adjuvants to enhance immunogenicity. An immunological adjuvant is a substance formulated with a vaccine to elevate the immune response to an antigen, such as the COVID‑19 virus or influenza virus. Specifically, an adjuvant may be used in formulating a COVID‑19 vaccine candidate to boost its immunogenicity and efficacy to reduce or prevent COVID‑19 infection in vaccinated individuals. Adjuvants used in COVID‑19 vaccine formulation may be particularly effective for technologies using the inactivated COVID‑19 virus and recombinant protein-based or vector-based vaccines. Aluminum salts, known as "alum", were the first adjuvant used for licensed vaccines, and are the adjuvant of choice in some 80% of adjuvanted vaccines. The alum adjuvant initiates diverse molecular and cellular mechanisms to enhance immunogenicity, including release of proinflammatory cytokines.

Clinical research

Main article: COVID-19 vaccine clinical research

These paragraphs are an excerpt from COVID-19 vaccine clinical research.[edit]

COVID-19 vaccine clinical research uses clinical research to establish the characteristics of COVID-19 vaccines. These characteristics include efficacy, effectiveness, and safety. As of November 2022, 40 vaccines are authorized by at least one national regulatory authority for public use:

As of June 2022, 353 vaccine candidates are in various stages of development, with 135 in clinical research, including 38 in phase I trials, 32 in phase I–II trials, 39 in phase III trials, and 9 in phase IV development.

Post-vaccination complications

Main article: Embolic and thrombotic events after COVID-19 vaccination

These paragraphs are an excerpt from Embolic and thrombotic events after COVID-19 vaccination.[edit]

Post-vaccination embolic and thrombotic events, termed vaccine-induced immune thrombotic thrombocytopenia (VITT), vaccine-induced prothrombotic immune thrombocytopenia (VIPIT), thrombosis with thrombocytopenia syndrome (TTS), vaccine-induced immune thrombocytopenia and thrombosis (VITT), or vaccine-associated thrombotic thrombocytopenia (VATT), are rare types of blood clotting syndromes that were initially observed in a number of people who had previously received the Oxford–AstraZeneca COVID‑19 vaccine (AZD1222) during the COVID‑19 pandemic. It was subsequently also described in the Janssen COVID‑19 vaccine (Johnson & Johnson), leading to the suspension of its use until its safety had been reassessed. On 5 May 2022 the FDA posted a bulletin limiting the use of the Janssen Vaccine to very specific cases due to further reassessment of the risks of TTS, although the FDA also stated in the same bulletin that the benefits of the vaccine outweigh the risks.

In April 2021, AstraZeneca and the European Medicines Agency (EMA) updated their information for healthcare professionals about AZD1222, saying it is "considered plausible" that there is a causal relationship between the vaccination and the occurrence of thrombosis in combination with thrombocytopenia and that, "although such adverse reactions are very rare, they exceeded what would be expected in the general population". AstraZeneca initially denied the link, saying "we do not accept that TTS is caused by the vaccine at a generic level". However, in legal documents filed in February 2024, AstraZeneca finally admitted its vaccine 'can, in very rare cases, cause TTS'.

Vaccine types

Conceptual diagram showing three vaccine types for forming SARS‑CoV‑2 proteins to prompt an immune response: (1) RNA vaccine, (2) subunit vaccine, (3) viral vector vaccine

Vaccine platforms being employed for SARS-CoV-2. Whole virus vaccines include both attenuated and inactivated forms of the virus. Protein and peptide subunit vaccines are usually combined with an adjuvant in order to enhance immunogenicity. The main emphasis in SARS-CoV-2 vaccine development has been on using the whole spike protein in its trimeric form, or components of it, such as the RBD region. Multiple non-replicating viral vector vaccines have been developed, particularly focused on adenovirus, while there has been less emphasis on the replicating viral vector constructs.

At least nine different technology platforms are under research and development to create an effective vaccine against COVID‑19. Most of the platforms of vaccine candidates in clinical trials are focused on the coronavirus spike protein and its variants as the primary antigen of COVID‑19 infection, since the S protein triggers immune responses. Platforms being developed in 2020 involved nucleic acid technologies (nucleoside-modified messenger RNA and DNA), non-replicating viral vectors, peptides, recombinant proteins, live attenuated viruses, and inactivated viruses.

Many vaccine technologies being developed for COVID‑19 are not like vaccines already in use to prevent influenza, but rather are using "next-generation" strategies for precise targeting of COVID‑19 infection mechanisms. Several of the synthetic vaccines use a 2P mutation to lock the spike protein into its prefusion configuration, stimulating an adaptive immune response to the virus before it attaches to a human cell. Vaccine platforms in development may improve flexibility for antigen manipulation, and effectiveness for targeting mechanisms of COVID‑19 infection in susceptible population subgroups, such as healthcare workers, the elderly, children, pregnant women, and people with weakened immune systems.

RNA vaccines

Further information: RNA vaccine

Diagram of the operation of an RNA vaccine. Messenger RNA contained in the vaccine enters cells and is translated into foreign proteins, which trigger an immune response.

Several COVID-19 vaccines, including the Pfizer–BioNTech and Moderna vaccines, have been developed to use RNA to stimulate an immune response. When introduced into human tissue, the RNA contained in the vaccine acts as messenger RNA (mRNA) to cause cells to build the SARS-CoV-2 spike protein. This teaches the body how to identify and destroy the corresponding pathogen. RNA vaccines often, but not always, use nucleoside-modified messenger RNA. The delivery of mRNA is achieved by a coformulation of the molecule into lipid nanoparticles which protect the RNA strands and help their absorption into the cells.

RNA vaccines were the first COVID‑19 vaccines to be authorized in the United Kingdom, the United States and the European Union. Authorized vaccines of this type are the Pfizer–BioNTech and Moderna vaccines. The CVnCoV RNA vaccine from CureVac failed in clinical trails.

Severe allergic reactions are rare. In December 2020, 1,893,360 first doses of Pfizer–BioNTech COVID‑19 vaccine administration resulted in 175 cases of severe allergic reaction, of which 21 were anaphylaxis. For 4,041,396 Moderna COVID‑19 vaccine dose administrations in December 2020 and January 2021, only ten cases of anaphylaxis were reported. The lipid nanoparticles were most likely responsible for the allergic reactions.

Adenovirus vector vaccines

These vaccines are examples of non-replicating viral vector vaccines, using an adenovirus shell containing DNA that encodes a SARS‑CoV‑2 protein. The viral vector-based vaccines against COVID‑19 are non-replicating, meaning that they do not make new virus particles, but rather produce only the antigen which elicits a systemic immune response.

Authorized vaccines of this type are the Oxford–AstraZeneca COVID-19 vaccine, the Sputnik V COVID-19 vaccine, Convidecia, and the Janssen COVID-19 vaccine.

Convidecia and the Janssen COVID-19 vaccine are both one-shot vaccines which offer less complicated logistics and can be stored under ordinary refrigeration for several months.

Sputnik V uses Ad26 for its first dose, which is the same as Janssen's only dose, and Ad5 for the second dose, which is the same as Convidecia's only dose.

On 11 August 2021, the developers of Sputnik V proposed, in view of the Delta case surge that Pfizer test the Ad26 component (termed its ‘Light’ version) as a booster shot:

Delta cases surge in US & Israel shows mRNA vaccines need a heterogeneous booster to strengthen & prolong immune response. #SputnikV pioneered mix&match approach, combo trials & showed 83.1% efficacy vs Delta. Today RDIF offers Pfizer to start trial with Sputnik Light as booster.

Inactivated virus vaccines

Inactivated vaccines consist of virus particles that have been grown in culture and then are killed using a method such as heat or formaldehyde to lose disease producing capacity, while still stimulating an immune response.

Authorized vaccines of this type are the Chinese CoronaVac, BBIBP-CorV, and WIBP-CorV; the Indian Covaxin; later this year the Russian CoviVac; the Kazakhstani vaccine QazVac; and the Iranian COVIran Barekat. Vaccines in clinical trials include the Valneva COVID-19 vaccine.

Subunit vaccines

Subunit vaccines present one or more antigens without introducing whole pathogen particles. The antigens involved are often protein subunits, but can be any molecule that is a fragment of the pathogen.

The three authorized vaccines of this type are the peptide vaccine EpiVacCorona, ZF2001, and MVC-COV1901. Vaccines with pending authorizations include the Novavax COVID-19 vaccine, Soberana 02 (a conjugate vaccine), and the Sanofi–GSK vaccine.

The V451 vaccine was previously in clinical trials, which were terminated because it was found that the vaccine may potentially cause incorrect results for subsequent HIV testing.

Intranasal

Intranasal vaccines target mucosal immunity in the nasal mucosa which is a portal for viral entrance to the body. These vaccines are designed to stimulate nasal immune factors, such as IgA. In addition to inhibiting the virus, nasal vaccines provide ease of administration because no needles (and the accompanying needle phobia) are involved. Nasal vaccines have been approved for other infections, such as influenza. As of 2021, only one nasal vaccine, Flumist (USA); Fluenz Tetra (European Union), had been authorized in the United States and Europe for use as an influenza vaccine.

Other types

Additional types of vaccines that are in clinical trials include virus-like particle vaccines, multiple DNA plasmid vaccines, at least two lentivirus vector vaccines, a conjugate vaccine, and a vesicular stomatitis virus displaying the SARS‑CoV‑2 spike protein.

Scientists investigated whether existing vaccines for unrelated conditions could prime the immune system and lessen the severity of COVID‑19 infection. There is experimental evidence that the BCG vaccine for tuberculosis has non-specific effects on the immune system, but no evidence that this vaccine is effective against COVID‑19.

Planning and development

Main article: History of COVID-19 vaccine development

Since January 2020, vaccine development has been expedited via unprecedented collaboration in the multinational pharmaceutical industry and between governments.

Multiple steps along the entire development path are evaluated, including:

• the level of acceptable toxicity of the vaccine (its safety),
• targeting vulnerable populations,
• the need for vaccine efficacy breakthroughs,
• the duration of vaccination protection,
• special delivery systems (such as oral or nasal, rather than by injection),
• dose regimen,
• stability and storage characteristics,
• emergency use authorization before formal licensing,
• optimal manufacturing for scaling to billions of doses, and
• dissemination of the licensed vaccine.

Challenges

There have been several unique challenges with COVID‑19 vaccine development.

The urgency to create a vaccine for COVID‑19 led to compressed schedules that shortened the standard vaccine development timeline, in some cases combining clinical trial steps over months, a process typically conducted sequentially over years. Public health programs have been described as in "[a] race to vaccinate individuals" with the early wave vaccines.

Timelines for conducting clinical research – normally a sequential process requiring years – are being compressed into safety, efficacy, and dosing trials running simultaneously over months, potentially compromising safety assurance. As an example, Chinese vaccine developers and the government Chinese Center for Disease Control and Prevention began their efforts in January 2020, and by March were pursuing numerous candidates on short timelines, with the goal to showcase Chinese technology strengths over those of the United States, and to reassure the Chinese people about the quality of vaccines produced in China.

The rapid development and urgency of producing a vaccine for the COVID‑19 pandemic may increase the risks and failure rate of delivering a safe, effective vaccine. Additionally, research at universities is obstructed by physical distancing and closing of laboratories.

Vaccines must progress through several phases of clinical trials to test for safety, immunogenicity, effectiveness, dose levels and adverse effects of the candidate vaccine. Vaccine developers have to invest resources internationally to find enough participants for Phase II–III clinical trials when the virus has proved to be a "moving target" of changing transmission rates across and within countries, forcing companies to compete for trial participants. Clinical trial organizers also may encounter people unwilling to be vaccinated due to vaccine hesitancy or disbelief in the science of the vaccine technology and its ability to prevent infection. As new vaccines are developed during the COVID‑19 pandemic, licensure of COVID‑19 vaccine candidates requires submission of a full dossier of information on development and manufacturing quality.

Organizations

Internationally, the Access to COVID-19 Tools Accelerator is a G20 and World Health Organization (WHO) initiative announced in April 2020. It is a cross-discipline support structure to enable partners to share resources and knowledge. It comprises four pillars, each managed by two to three collaborating partners: Vaccines (also called "COVAX"), Diagnostics, Therapeutics, and Health Systems Connector. The WHO's April 2020 "R&D Blueprint (for the) novel Coronavirus" documented a "large, international, multi-site, individually randomized controlled clinical trial" to allow "the concurrent evaluation of the benefits and risks of each promising candidate vaccine within 3–6 months of it being made available for the trial." The WHO vaccine coalition will prioritize which vaccines should go into Phase II and III clinical trials, and determine harmonized Phase III protocols for all vaccines achieving the pivotal trial stage.

National governments have also been involved in vaccine development. Canada announced funding for 96 research vaccine research projects at Canadian companies and universities, with plans to establish a "vaccine bank" that could be used if another coronavirus outbreak occurs, and to support clinical trials and develop manufacturing and supply chains for vaccines.

China provided low-rate loans to one vaccine developer through its central bank, and "quickly made land available for the company" to build production plants. Three Chinese vaccine companies and research institutes are supported by the government for financing research, conducting clinical trials, and manufacturing.

Great Britain formed a COVID‑19 vaccine task force in April 2020 to stimulate local efforts for accelerated development of a vaccine through collaborations of industry, universities, and government agencies. It encompassed every phase of development from research to manufacturing.

In the United States, the Biomedical Advanced Research and Development Authority (BARDA), a federal agency funding disease-fighting technology, announced investments to support American COVID‑19 vaccine development, and manufacture of the most promising candidates. In May 2020, the government announced funding for a fast-track program called Operation Warp Speed. By March 2021, BARDA had funded an estimated $19.3 billion in COVID-19 vaccine development.

Large pharmaceutical companies with experience in making vaccines at scale, including Johnson & Johnson, AstraZeneca, and GlaxoSmithKline (GSK), formed alliances with biotechnology companies, governments, and universities to accelerate progression towards effective vaccines.

History

This section is an excerpt from History of COVID-19 vaccine development.[edit]

COVID‑19 vaccine research samples in a NIAID lab freezer (30 January 2020)

SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), the virus that causes COVID-19, was isolated in late 2019. Its genetic sequence was published on 11 January 2020, triggering an urgent international response to prepare for an outbreak and hasten the development of a preventive COVID-19 vaccine. Since 2020, vaccine development has been expedited via unprecedented collaboration in the multinational pharmaceutical industry and between governments. By June 2020, tens of billions of dollars were invested by corporations, governments, international health organizations, and university research groups to develop dozens of vaccine candidates and prepare for global vaccination programs to immunize against COVID‑19 infection. According to the Coalition for Epidemic Preparedness Innovations (CEPI), the geographic distribution of COVID‑19 vaccine development shows North American entities to have about 40% of the activity, compared to 30% in Asia and Australia, 26% in Europe, and a few projects in South America and Africa.

In February 2020, the World Health Organization (WHO) said it did not expect a vaccine against SARS‑CoV‑2 to become available in less than 18 months. Virologist Paul Offit commented that, in hindsight, the development of a safe and effective vaccine within 11 months was a remarkable feat. The rapidly growing infection rate of COVID‑19 worldwide during 2020 stimulated international alliances and government efforts to urgently organize resources to make multiple vaccines on shortened timelines, with four vaccine candidates entering human evaluation in March (see COVID-19 vaccine § Trial and authorization status).

On 24 June 2020, China approved the CanSino vaccine for limited use in the military and two inactivated virus vaccines for emergency use in high-risk occupations. On 11 August 2020, Russia announced the approval of its Sputnik V vaccine for emergency use, though one month later only small amounts of the vaccine had been distributed for use outside of the phase 3 trial.

The Pfizer–BioNTech partnership submitted an Emergency Use Authorization (EUA) request to the U.S. Food and Drug Administration (FDA) for the mRNA vaccine BNT162b2 (active ingredient tozinameran) on 20 November 2020. On 2 December 2020, the United Kingdom's Medicines and Healthcare products Regulatory Agency (MHRA) gave temporary regulatory approval for the Pfizer–BioNTech vaccine, becoming the first country to approve the vaccine and the first country in the Western world to approve the use of any COVID‑19 vaccine. As of 21 December 2020, many countries and the European Union had authorized or approved the Pfizer–BioNTech COVID‑19 vaccine. Bahrain and the United Arab Emirates granted emergency marketing authorization for the Sinopharm BIBP vaccine. On 11 December 2020, the FDA granted an EUA for the Pfizer–BioNTech COVID‑19 vaccine. A week later, they granted an EUA for mRNA-1273 (active ingredient elasomeran), the Moderna vaccine.

On 31 March 2021, the Russian government announced that they had registered the first COVID‑19 vaccine for animals. Named Carnivac-Cov, it is an inactivated vaccine for carnivorous animals, including pets, aimed at preventing mutations that occur during the interspecies transmission of SARS-CoV-2.

In October 2022, China began administering an oral vaccine developed by CanSino Biologics using its adenovirus model.

Despite the availability of mRNA and viral vector vaccines, worldwide vaccine equity has not been achieved. The ongoing development and use of whole inactivated virus (WIV) and protein-based vaccines has been recommended, especially for use in developing countries, to dampen further waves of the pandemic.

In June 2021, a report revealed that the UB-612 vaccine, developed by the US-based COVAXX, was a venture initiated for profits by the Blackwater founder Erik Prince. In a series of text messages to Paul Behrends, the close associate recruited for the COVAXX project, Prince described the profit-making possibilities in selling the COVID‑19 vaccines. COVAXX provided no data from the clinical trials on safety or efficacy. The responsibility of creating distribution networks was assigned to an Abu Dhabi-based entity, which was mentioned as "Windward Capital" on the COVAXX letterhead but was actually Windward Holdings. The sole shareholder of the firm, which handled "professional, scientific and technical activities", was Erik Prince. In March 2021, COVAXX raised $1.35 billion in a private placement.

Effectiveness

This section is an excerpt from COVID-19 vaccine clinical research § Effectiveness.[edit]

Evidence from vaccine use during the pandemic shows vaccination can reduce infection and is most effective at preventing severe COVID-19 symptoms and death, but is less good at preventing mild COVID-19. Efficacy wanes over time but can be maintained with boosters. In 2021, the CDC reported that unvaccinated people were 10 times more likely to be hospitalized and 11 times more likely to die than fully vaccinated people.

The CDC reported that vaccine effectiveness fell from 91% against Alpha to 66% against Delta. One expert stated that "those who are infected following vaccination are still not getting sick and not dying like was happening before vaccination." By late August 2021, the Delta variant accounted for 99 percent of U.S. cases and was found to double the risk of severe illness and hospitalization for those not yet vaccinated.

In November 2021, a study by the ECDC estimated that 470,000 lives over the age of 60 had been saved since the start of the vaccination roll-out in the European region.

On 10 December 2021, the UK Health Security Agency reported that early data indicated a 20- to 40-fold reduction in neutralizing activity for Omicron by sera from Pfizer 2-dose vaccinees relative to earlier strains. After a booster dose (usually with an mRNA vaccine), vaccine effectiveness against symptomatic disease was at 70%–75%, and the effectiveness against severe disease was expected to be higher.

According to early December 2021 CDC data, "unvaccinated adults were about 97 times more likely to die from COVID-19 than fully vaccinated people who had received boosters".

A meta-analysis looking into COVID-19 vaccine differences in immunosuppressed individuals found that people with a weakened immune system are less able to produce neutralizing antibodies. For example, organ transplant recipients need three vaccines to achieve seroconversion. A study on the serologic response to mRNA vaccines among patients with lymphoma, leukemia, and myeloma found that one-quarter of patients did not produce measurable antibodies, varying by cancer type.

In February 2023, a systematic review in The Lancet said that the protection afforded by infection was comparable to that from vaccination, albeit with an increased risk of severe illness and death from the disease of an initial infection.

A January 2024 study by the CDC found that staying up to date on the vaccines could reduce the risk of strokes, blood clots and heart attacks related to COVID-19 in people aged 65 years or older or with a condition that makes them more vulnerable to said conditions.

Side effects

Serious adverse events associated with receipt of new vaccines targeting COVID-19 are of high interest to the public. All vaccines that are administered via intramuscular injection, including COVID-19 vaccines, have side effects related to the mild trauma associated with the procedure and introduction of a foreign substance into the body. These include soreness, redness, rash, and inflammation at the injection site. Other common side effects include fatigue, headache, myalgia (muscle pain), and arthralgia (joint pain) which generally resolve within a few days. One less-frequent side effect (that generally occurs in less than 1 in 1,000 people) is hypersensitivity (allergy) to one or more of the vaccine's ingredients, which in some rare cases may cause anaphylaxis.

Society and culture

Distribution

Note about table to the right: Number and percentage of people who have received at least one dose of a COVID-19 vaccine (unless noted otherwise). May include vaccination of non-citizens, which can push totals beyond 100% of the local population. Table is updated daily by a bot.

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Updated June 7, 2024.

COVID-19 vaccine distribution by country

	Location	Vaccinated	Percent
	World	5,631,262,584	70.61%
	China	1,310,292,000	91.89%
	India	1,027,438,679	72.50%
	European Union	338,119,452	75.11%
	United States	270,227,181	81.39%
	Indonesia	203,878,473	74.00%
	Brazil	189,643,431	88.08%
	Pakistan	165,567,890	70.21%
	Bangladesh	151,507,159	88.50%
	Japan	104,705,133	84.47%
	Mexico	97,179,493	76.22%
	Nigeria	92,261,510	42.22%
	Vietnam	90,272,853	91.94%
	Russia	89,081,596	61.56%
	Philippines	78,484,848	67.92%
	Iran	65,199,831	73.63%
	Germany	64,876,299	77.82%
	Turkey	57,941,051	67.89%
	Thailand	57,005,497	79.62%
	Egypt	56,907,319	51.27%
	France	54,677,678	80.63%
	United Kingdom	53,806,963	79.97%
	Italy	50,936,719	86.28%
	South Korea	44,784,499	86.43%
	Ethiopia	44,073,766	35.72%
	Colombia	43,012,174	82.92%
	Argentina	41,529,058	91.25%
	Spain	41,351,234	86.95%
	Myanmar	34,777,314	64.64%
	Canada	34,763,194	90.40%
	Tanzania	34,434,933	52.57%
	Peru	30,563,708	89.76%
	Malaysia	28,138,225	82.91%
	Nepal	27,883,196	91.28%
	Saudi Arabia	27,041,364	74.27%
	Morocco	25,020,168	66.80%
	South Africa	24,209,938	40.42%
	Poland	22,877,472	57.40%
	Mozambique	22,869,646	69.37%
	Australia	22,236,698	84.95%
	Venezuela	22,157,232	78.29%
	Taiwan	21,899,240	91.65%
	Uzbekistan	21,674,823	62.59%
	Uganda	19,488,104	41.25%
	Afghanistan	18,896,999	45.95%
	Chile	18,088,517	92.27%
	Sri Lanka	17,143,761	78.53%
	Angola	16,522,932	46.43%
	Ukraine	15,729,617	36.19%
	Democratic Republic of the Congo	15,388,889	15.54%
	Ecuador	15,333,873	85.18%
	Cambodia	15,315,251	91.34%
	Sudan	15,207,452	32.44%
	Kenya	14,494,372	26.83%
	Ivory Coast	13,568,372	48.18%
	Ghana	13,221,421	39.50%
	Netherlands	12,596,446	71.72%
	Zambia	11,637,730	58.14%
	Iraq	11,332,925	25.47%
	Kazakhstan	10,858,101	55.98%
	Cuba	10,805,570	96.37%
	Rwanda	10,572,981	76.75%
	United Arab Emirates	9,991,089	100.00%
	Portugal	9,791,341	95.33%
	Belgium	9,267,479	79.51%
	Somalia	8,972,167	50.99%
	Guatemala	8,933,623	50.07%
	Romania	8,187,976	41.65%
	Greece	7,937,992	76.44%
	Algeria	7,840,131	17.75%
	Sweden	7,775,726	73.71%
	Guinea	7,679,918	55.41%
	Dominican Republic	7,367,193	65.61%
	Bolivia	7,361,008	60.94%
	Tunisia	7,218,871	58.42%
	Czech Republic	6,981,981	66.53%
	Hong Kong	6,919,667	92.40%
	Austria	6,899,873	77.18%
	Israel	6,723,119	71.15%
	Honduras	6,596,213	63.23%
	Belarus	6,527,591	68.46%
	Zimbabwe	6,437,808	40.25%
	Hungary	6,420,813	64.42%
	Nicaragua	6,260,823	90.10%
	Chad	6,254,729	35.29%
	Niger	6,217,508	23.72%
	Switzerland	6,096,911	69.75%
	Burkina Faso	6,089,089	26.86%
	Laos	5,888,649	79.31%
	Azerbaijan	5,373,253	52.10%
	Malawi	5,343,858	26.19%
	Tajikistan	5,282,863	54.18%
	Sierra Leone	5,252,127	61.03%
	Singapore	5,160,551	91.55%
	Jordan	4,821,579	43.25%
	Denmark	4,752,101	80.79%
	El Salvador	4,652,597	73.69%
	Costa Rica	4,641,899	89.60%
	Finland	4,524,288	81.65%
	Mali	4,354,292	19.27%
	Norway	4,346,995	79.99%
	New Zealand	4,301,605	82.96%
	South Sudan	4,287,160	39.28%
	Republic of Ireland	4,112,237	81.87%
	Paraguay	3,993,938	58.90%
	Liberia	3,825,381	72.14%
	Cameroon	3,753,733	13.45%
	Benin	3,697,190	27.69%
	Panama	3,533,477	80.15%
	Kuwait	3,457,498	80.99%
	Serbia	3,354,075	48.81%
	Syria	3,295,630	14.90%
	Oman	3,257,365	71.18%
	Uruguay	3,010,451	87.95%
	Qatar	2,852,178	105.83%
	Slovakia	2,822,919	51.82%
	Lebanon	2,740,227	49.92%
	Madagascar	2,700,391	9.12%
	Senegal	2,684,696	15.50%
	Central African Republic	2,600,389	46.61%
	Croatia	2,323,025	57.64%
	Libya	2,316,327	34.00%
	Mongolia	2,272,965	68.27%
	Togo	2,255,579	25.49%
	Bulgaria	2,108,377	31.09%
	Mauritania	2,103,754	44.42%
	Palestine	2,012,767	38.34%
	Lithuania	1,958,287	71.21%
	Botswana	1,951,054	74.18%
	Kyrgyzstan	1,736,541	26.19%
	Georgia	1,654,504	44.03%
	Albania	1,348,396	47.44%
	Latvia	1,346,184	71.84%
	Slovenia	1,265,802	59.72%
	Bahrain	1,241,174	84.31%
	Mauritius	1,123,773	86.48%
	Armenia	1,122,040	40.35%
	Moldova	1,108,879	33.88%
	Yemen	1,050,112	3.12%
	Lesotho	1,014,073	43.98%
	Bosnia and Herzegovina	943,394	28.91%
	Gambia	934,799	34.55%
	Kosovo	906,858	50.89%
	Timor-Leste	886,838	66.12%
	Estonia	870,180	65.62%
	Jamaica	859,773	30.41%
	North Macedonia	854,570	40.82%
	Trinidad and Tobago	753,588	49.39%
	Guinea-Bissau	747,057	35.48%
	Fiji	712,025	76.58%
	Bhutan	699,116	89.35%
	Republic of the Congo	695,760	11.92%
	Macau	679,703	97.77%
	Cyprus	670,969	74.88%
	Namibia	629,767	24.53%
	Eswatini	526,050	43.78%
	Haiti	521,396	4.50%
	Guyana	495,285	61.24%
	Luxembourg	481,957	74.42%
	Malta	478,953	89.81%
	Brunei	451,149	100.48%
	Comoros	438,825	53.41%
	Djibouti	421,573	37.61%
	Maldives	399,308	76.23%
	Papua New Guinea	382,020	3.77%
	Cabo Verde	356,734	60.68%
	Solomon Islands	343,821	47.47%
	Gabon	311,040	13.02%
	Iceland	309,770	84.00%
	Northern Cyprus	301,673	78.80%
	Montenegro	292,783	46.63%
	Equatorial Guinea	270,109	16.53%
	Suriname	267,820	45.26%
	Belize	258,473	63.78%
	New Caledonia	192,375	66.35%
	Samoa	191,403	86.07%
	French Polynesia	190,908	62.33%
	Vanuatu	176,624	54.06%
	Bahamas	174,810	42.64%
	Barbados	163,846	58.17%
	Sao Tome and Principe	140,256	61.68%
	Curaçao	108,601	56.81%
	Kiribati	100,900	76.88%
	Aruba	90,546	85.05%
	Seychelles	88,520	82.62%
	Tonga	87,342	81.73%
	Jersey	84,365	76.14%
	Isle of Man	69,560	81.44%
	Antigua and Barbuda	64,290	68.97%
	Cayman Islands	62,023	90.25%
	Saint Lucia	60,140	33.43%
	Andorra	57,901	72.52%
	Guernsey	54,223	85.62%
	Bermuda	48,554	75.65%
	Grenada	44,241	35.26%
	Gibraltar	42,175	129.07%
	Faroe Islands	41,715	85.04%
	Greenland	41,243	72.52%
	Saint Vincent and the Grenadines	37,527	36.10%
	Burundi	36,909	0.29%
	Saint Kitts and Nevis	33,794	70.88%
	Dominica	32,995	45.57%
	Turks and Caicos Islands	32,815	71.76%
	Turkmenistan	32,240	0.53%
	Sint Maarten	29,788	67.41%
	Liechtenstein	26,771	68.02%
	Monaco	26,672	67.49%
	San Marino	26,357	77.50%
	British Virgin Islands	19,466	62.55%
	Caribbean Netherlands	19,109	72.26%
	Cook Islands	15,112	88.73%
	Nauru	13,106	103.27%
	Anguilla	10,854	68.36%
	Wallis and Futuna	7,150	61.66%
	Tuvalu	6,368	53.40%
	Saint Helena, Ascension and Tristan da Cunha	4,361	71.83%
	Falkland Islands	2,632	75.57%
	Tokelau	2,203	116.38%
	Montserrat	2,104	47.68%
	Niue	1,650	102.23%
	Pitcairn Islands	47	100.00%
	North Korea	0	0.00%

Main article: Deployment of COVID-19 vaccines

These paragraphs are an excerpt from Deployment of COVID-19 vaccines.[edit]

As of 3 January 2024, 13.53 billion COVID-19 vaccine doses have been administered worldwide, with 70.6 percent of the global population having received at least one dose. While 4.19 million vaccines were then being administered daily, only 22.3 percent of people in low-income countries had received at least a first vaccine by September 2022, according to official reports from national health agencies, which are collated by Our World in Data.

During a pandemic on the rapid timeline and scale of COVID-19 cases in 2020, international organizations like the World Health Organization (WHO) and Coalition for Epidemic Preparedness Innovations (CEPI), vaccine developers, governments, and industry evaluated the distribution of the eventual vaccine(s). Individual countries producing a vaccine may be persuaded to favor the highest bidder for manufacturing or provide first-class service to their own country. Experts emphasize that licensed vaccines should be available and affordable for people at the frontlines of healthcare and in most need.

In April 2020, it was reported that the UK agreed to work with 20 other countries and global organizations, including France, Germany, and Italy, to find a vaccine and share the results, and that UK citizens would not get preferential access to any new COVID‑19 vaccines developed by taxpayer-funded UK universities. Several companies planned to initially manufacture a vaccine at artificially low prices, then increase prices for profitability later if annual vaccinations are needed and as countries build stock for future needs.

The WHO had set out the target to vaccinate 40% of the population of all countries by the end of 2021 and 70% by mid-2022, but many countries missed the 40% target at the end of 2021.

• 
  Share of people who have received at least one dose of a COVID-19 vaccine relative to a country's total population. Date is at the bottom of the map. Commons source.
• 
  COVID-19 vaccine doses administered per 100 people by country. Date is at the bottom of the map. Commons source.

Access

Further information: Deployment of COVID-19 vaccines § Equitable access

Nations pledged to buy doses of COVID‑19 vaccine before the doses were available. Though high-income nations represent only 14% of the global population, as of 15 November 2020, they had contracted to buy 51% of all pre-sold doses. Some high-income nations bought more doses than would be necessary to vaccinate their entire populations.

Production of Sputnik V vaccine in Brazil, January 2021.

An elderly man receiving second dose of CoronaVac vaccine in Brazil, April 2021.

On 18 January 2021, WHO Director-General Tedros Adhanom Ghebreyesus warned of problems with equitable distribution: "More than 39 million doses of vaccine have now been administered in at least 49 higher-income countries. Just 25 doses have been given in one lowest-income country. Not 25 million; not 25 thousand; just 25."

In March, it was revealed the US attempted to convince Brazil not to purchase the Sputnik V COVID-19 vaccine, fearing "Russian influence" in Latin America. Some nations involved in long-standing territorial disputes have reportedly had their access to vaccines blocked by competing nations; Palestine has accused Israel of blocking vaccine delivery to Gaza, while Taiwan has suggested that China has hampered its efforts to procure vaccine doses.

A single dose of the COVID‑19 vaccine by AstraZeneca would cost 47 Egyptian pounds (EGP) and the authorities are selling it between 100 and 200 EGP. A report by Carnegie Endowment for International Peace cited the poverty rate in Egypt as around 29.7 percent, which constitutes approximately 30.5 million people, and claimed that about 15 million of the Egyptians would be unable to gain access to the luxury of vaccination. A human rights lawyer, Khaled Ali, launched a lawsuit against the government, forcing them to provide vaccination free of cost to all members of the public.

According to immunologist Dr. Anthony Fauci, mutant strains of virus and limited vaccine distribution pose continuing risks and he said: "we have to get the entire world vaccinated, not just our own country." Edward Bergmark and Arick Wierson are calling for a global vaccination effort and wrote that the wealthier nations' "me-first" mentality could ultimately backfire, because the spread of the virus in poorer countries would lead to more variants, against which the vaccines could be less effective.

On 10 March 2021, the United States, Britain, European Union nations and other WTO members blocked a push by more than eighty developing countries to waive COVID‑19 vaccine patent rights in an effort to boost production of vaccines for poor nations. On 5 May 2021, the Biden administration announced that it supports waiving intellectual property protections for COVID-19 vaccines. The Members of the European Parliament have backed a motion demanding the temporary lifting of intellectual properties rights for COVID‑19 vaccines. Commission vice-president Valdis Dombrovskis, stressed that while the EU is ready to discuss the issue of patent waivers, its proposed solutions include limiting export restrictions, resolving production bottlenecks, looking into compulsory licensing, investing in manufacturing capacity in developing countries and increasing contributions to the COVAX scheme.

COVID-19 mass vaccination queue in Finland, June 2021.

A drive-through COVID-19 vaccination center in Iran, August 2021.

In a meeting in April 2021, the World Health Organization's emergency committee addressed concerns of persistent inequity in the global vaccine distribution. Although 9 percent of the world's population lives in the 29 poorest countries, these countries had received only 0.3% of all vaccines administered as of May 2021. On 15 March, Brazilian journalism agency Agência Pública reported that the country vaccinated about twice as many people who declare themselves white than black and noted that mortality from COVID-19 is higher in the black population.

In May 2021, UNICEF made an urgent appeal to industrialised nations to pool their excess COVID-19 vaccine capacity to make up for a 125-million-dose gap in the COVAX program. The program mostly relied on the Oxford–AstraZeneca COVID-19 vaccine produced by Serum Institute of India, which faced serious supply problems due to increased domestic vaccine needs in India from March to June 2021. Only a limited amount of vaccines can be distributed efficiently, and the shortfall of vaccines in South America and parts of Asia are due to a lack of expedient donations by richer nations. International aid organisations have pointed at Nepal, Sri Lanka, and Maldives as well as Argentina and Brazil, and some parts of the Caribbean as problem areas, where vaccines are in short supply. In mid-May 2021, UNICEF was also critical of the fact that most proposed donations of Moderna and Pfizer vaccines were not slated for delivery until the second half of 2021, or early 2022.

On 1 July 2021, the heads of the World Bank Group, International Monetary Fund, World Health Organization and World Trade Organization said in a joint statement: "As many countries are struggling with new variants and a third wave of COVID-19 infections, accelerating access to vaccines becomes even more critical to ending the pandemic everywhere and achieving broad-based growth. We are deeply concerned about the limited vaccines, therapeutics, diagnostics, and support for deliveries available to developing countries." In July 2021, The BMJ reported that countries have thrown out over 250,000 vaccine doses as supply exceeded demand and strict laws prevented the sharing of vaccines. A survey by The New York Times found that over a million doses of vaccine had been thrown away in ten U.S. states because federal regulations prohibit recalling them, preventing their redistribution abroad. Furthermore, doses donated close to expiration often cannot be administered quickly enough by recipient countries and end up having to be discarded.

Amnesty International and Oxfam International have criticized the support of vaccine monopolies by the governments of producing countries, noting that this is dramatically increasing the dose price by 5 times and often much more, creating an economic barrier to access for poor countries. Médecins Sans Frontières (Doctors without Borders) has also criticized vaccine monopolies and repeatedly called from their suspension, supporting the TRIPS Waiver. The waiver was first proposed in October 2020, and has support from most countries, but delayed by opposition EU (especially Germany), UK, Norway and Switzerland, among others. MSF called for a Day of Action in September 2021 to put pressure on the WTO Minister's meeting in November, which is expected to discuss the TRIPS IP waiver.

On 4 August 2021, to reduce unequal distribution between rich and poor countries, the WHO called for a moratorium on a booster dose at least until the end of September. However, on 18 August, the United States government announced plans to offer booster doses 8 months after the initial course to the general population, starting with priority groups. Before the announcement, the WHO harshly criticized this type of decision, citing the lack of evidence for the need for boosters, except for patients with specific conditions. At this time, vaccine coverage of at least one dose was 58% in high-income countries and only 1.3% in low-income countries, and 1.14 million Americans already received an unauthorized booster dose. US officials argued that waning efficacy against mild and moderate disease might indicate reduced protection against severe disease in the coming months. Israel, France, Germany and the United Kingdom have also started planning boosters for specific groups. On 14 September 2021, more than 140 former world leaders, and Nobel laureates, including former President of France François Hollande, former Prime Minister of the United Kingdom Gordon Brown, former Prime Minister of New Zealand Helen Clark, and Professor Joseph Stiglitz, called on the candidates to be the next German chancellor to declare themselves in favour of waiving intellectual property rules for COVID-19 vaccines and transferring vaccine technologies.

Optimizing the societal benefit of vaccination may benefit from a strategy that is tailored to the state of the pandemic, the demographics of a country, the age of the recipients, the availability of vaccines, and the individual risk for severe disease: In the UK, the interval between prime and boost dose was extended to vaccinate as many persons as early as possible, many countries are starting to give an additional booster shot to the immunosuppressed and the elderly, and research predicts an additional benefit of personalizing vaccine dose in the setting of limited vaccine availability when a wave of virus Variants of Concern hits a country.

While vaccines substantially reduce the probability of infection, it is still possible for fully vaccinated people to contract and spread COVID-19. Public health agencies have recommended that vaccinated people continue using preventive measures (wear face masks, social distance, wash hands) to avoid infecting others, especially vulnerable people, particularly in areas with high community spread. Governments have indicated that such recommendations will be reduced as vaccination rates increase and community spread declines.

Inside of a vaccination center in Brussels, Belgium, February 2021.

Liability

Several governments agreed to shield pharmaceutical companies like Pfizer and Moderna from negligence claims related to COVID-19 vaccines (and treatments), as in previous pandemics, when governments also took on liability for such claims.

In the US, these liability shields took effect on 4 February 2020, when the US Secretary of Health and Human Services Alex Azar published a notice of declaration under the Public Readiness and Emergency Preparedness Act (PREP Act) for medical countermeasures against COVID‑19, covering "any vaccine, used to treat, diagnose, cure, prevent, or mitigate COVID‑19, or the transmission of SARS-CoV-2 or a virus mutating therefrom". The declaration precludes "liability claims alleging negligence by a manufacturer in creating a vaccine, or negligence by a health care provider in prescribing the wrong dose, absent willful misconduct". In other words, absent "willful misconduct", these companies can not be sued for money damages for any injuries that occur between 2020 and 2024 from the administration of vaccines and treatments related to COVID-19. The declaration is effective in the United States through 1 October 2024.

In December 2020, the UK government granted Pfizer legal indemnity for its COVID-19 vaccine.

In the European Union, the COVID‑19 vaccines are licensed under a Conditional Marketing Authorisation which does not exempt manufacturers from civil and administrative liability claims. While the purchasing contracts with vaccine manufacturers remain secret, they do not contain liability exemptions even for side-effects not known at the time of licensure.

The Bureau of Investigative Journalism, a nonprofit news organization, reported in an investigation that unnamed officials in some countries, such as Argentina and Brazil, said that Pfizer demanded guarantees against costs of legal cases due to adverse effects in the form of liability waivers and sovereign assets such as federal bank reserves, embassy buildings or military bases, going beyond the expected from other countries such as the US. During the pandemic parliamentary inquiry in Brazil, Pfizer's representative said that its terms for Brazil are the same as for all other countries with which it has signed deals.

Misinformation and hesitancy

Main article: COVID-19 vaccine misinformation and hesitancy

This section is an excerpt from COVID-19 vaccine misinformation and hesitancy.[edit]

In many countries a variety of unfounded conspiracy theories and other misinformation about COVID-19 vaccines have spread based on misunderstood or misrepresented science, religion, and law. These have included exaggerated claims about side effects, misrepresentations about how the immune system works and when and how COVID-19 vaccines are made, a story about COVID-19 being spread by 5G, and other false or distorted information. This misinformation, some created by anti-vaccination activists, has proliferated and may have made many people averse to vaccination. This has led to governments and private organizations around the world introducing measures to incentivize or coerce vaccination, such as lotteries, mandates, and free entry to events, which has in turn led to further misinformation about the legality and effect of these measures themselves.

In the US, some prominent biomedical scientists who publicly advocate vaccination have been attacked and threatened in emails and on social media by anti-vaccination activists.

Fake vaccines containing salt water have also been administered in some countries.

See also

• COVID-19 vaccine clinical research
• 2009 swine flu pandemic vaccine
• COVID-19 Vaccine Passport
• COVID-19 vaccine card
• COVID-19 drug development
• COVID-19 drug repurposing research

Further reading

• Krause PR, Fleming TR, Longini IM, Peto R, Briand S, Heymann DL, et al. (July 2021). "SARS-CoV-2 Variants and Vaccines". N Engl J Med. 385 (2): 179–86. doi:10.1056/NEJMsr2105280. PMC 8262623. PMID 34161052.
• Kyriakidis NC, López-Cortés A, González EV, Grimaldos AB, Prado EO (February 2021). "SARS-CoV-2 vaccines strategies: a comprehensive review of phase 3 candidates". NPJ Vaccines. 6 (1): 28. doi:10.1038/s41541-021-00292-w. PMC 7900244. PMID 33619260.
• Ramsay M, ed. (2020). "Chapter 14a: COVID-19". Immunisation against infectious disease. Public Health England.
• Development and Licensure of Vaccines to Prevent COVID-19: Guidance for Industry (PDF) (Report). U.S. Food and Drug Administration (FDA). June 2020. {{cite report}}: Unknown parameter |lay-url= ignored (help)

Vaccine protocols

• "Protocol mRNA-1273-P301" (PDF). Moderna.
• "Protocol C4591001 PF-07302048 (BNT162 RNA-Based COVID-19 Vaccines)" (PDF). Pfizer.
• "Protocol AZD1222 – D8110C00001" (PDF). AstraZeneca.
• "Protocol VAC31518COV3001; Phase 3 (ENSEMBLE)" (PDF). Janssen Vaccines & Prevention.
• "Protocol VAC31518COV3009; Phase 3 (ENSEMBLE 2)" (PDF). Janssen Vaccines & Prevention.
• "Protocol VAT00008 - Study of Monovalent and Bivalent Recombinant Protein Vaccines against COVID-19 in Adults 18 Years of Age and Older Protocol" (PDF). Sanofi Pasteur.

External links

• "The COVID-19 candidate vaccine landscape". World Health Organization (WHO).
• COVID‑19 Vaccine Tracker. Regulatory Affairs Professionals Society (RAPS)
• "STAT's Covid-19 Drugs and Vaccines Tracker". Stat. 27 April 2020.
• "COVID-19 vaccines: development, evaluation, approval and monitoring". European Medicines Agency (EMA).
• "Vaccine Development – 101". U.S. Food and Drug Administration (FDA). 27 August 2021.
• Corum J, Zimmer C (9 February 2021). "Coronavirus Variants and Mutations". The New York Times.
• M.I.T. Lecture 10: Kizzmekia Corbett, Vaccines" on YouTube
• "COVID-19 vaccines: research and development". European Medicines Agency (EMA).
• "The 5 Stages of COVID-19 Vaccine Development: What You Need to Know About How a Clinical Trial Works". Johnson & Johnson. 23 September 2020.
• "How patent laws get in the way of the global coronavirus vaccine rollout". The Conversation.
• Zimmer C, Sheikh K, Weiland N (20 May 2020). "A New Entry in the Race for a Coronavirus Vaccine: Hope". The New York Times.
• "Coronavirus vaccine - weekly summary of Yellow Card reporting". Medicines and Healthcare products Regulatory Agency (MHRA).
• "Joint Statement from HHS Public Health and Medical Experts on COVID-19 Booster Shots (08/18/2021)". Centers for Disease Control (CDC). 18 August 2021.
• CSPAN (video; 50:27) => White House COVID-19 Booster Announcement (08/18/2021)