|Target disease||Varicella (chickenpox), herpes zoster, postherpetic neuralgia, Ramsay Hunt syndrome type II|
|(what is this?)|
The varicella vaccine is a live (attenuated) virus administered to protect against the viral disease commonly known as chickenpox caused by the varicella zoster virus (VZV). The varicella vaccine is marketed as Varivax in the U.S. by Merck and globally as Varilrix by GlaxoSmithKline. Another vaccine that is known as Zostavax is simply a larger-than-normal dose of Varivax, and is used in older adults to reduce the risk of shingles (also called herpes zoster) and postherpetic neuralgia that are caused by the same virus.
It is on the World Health Organization's List of Essential Medicines, a list of the most important medication needed in a basic health system.
Varicella vaccine is 70% to 90% effective for preventing varicella and more than 95% effective for preventing severe varicella. Furthermore, follow-up evaluations took place in the United States of children immunized that revealed protection for at least 11 years. Also, studies were conducted in Japan which indicated protection for at least 20 years.
People who do not develop enough protection when they get the vaccine may develop a mild case of the disease when in close contact with a person with chickenpox. In these cases, people show very little sign of illness. This has been the case of children who get the vaccine in their early childhood and later have contact with children with chickenpox. Some of these children may develop a mild chickenpox also known as breakthrough disease.
Duration of immunity
The long-term duration of protection from varicella vaccine is unknown, but there are now persons vaccinated more than thirty years ago with no evidence of waning immunity, while others have become vulnerable in as few as six years. Assessments of duration of immunity are complicated in an environment where natural disease is still common, which typically leads to an overestimation of effectiveness.
Some vaccinated children have been found to lose their protective antibody in as little as five to eight years. However, according to the World Health Organization: "After observation of study populations for periods of up to 20 years in Japan and 10 years in the United States, more than 90% of immunocompetent persons who were vaccinated as children were still protected from varicella." However, since only one out of five Japanese children were vaccinated, the annual exposure of these vaccinees to children with natural chickenpox boosted the vaccinees' immune system. In the United States, where universal varicella vaccination has been practiced, the majority of children no longer receive exogenous (outside) boosting, thus, their cell-mediated immunity to VZV (varicella zoster virus) wanes—necessitating booster chickenpox vaccinations. Some persons exposed to the virus after vaccine can experience milder cases of chicken pox (and usually then harbor both the attenuated vaccine or oka strain as well as the wild type or natural chickenpox strain which are both subject to reactivation as shingles).
Catching "wild" chickenpox as a child has been thought to commonly result in lifelong immunity. Indeed, parents have deliberately ensured this in the past with "pox parties". Historically, exposure of adults to contagious children has boosted their immunity, reducing the risk of shingles.
The CDC and corresponding national organisations are carefully observing the failure rate which may be high compared with other modern vaccines—large outbreaks of chickenpox having occurred at schools which required their children to be vaccinated.
The mortality rate in immunocompromised patients with disseminated herpes zoster is 5–15%, with most deaths from pneumonia. Vaccines are less effective among these high-risk patients, as well as being more dangerous because they contain attenuated live virus (see last footnote). In a study performed on children with an impaired immune system, 30% had lost the antibody after five years, and 8% had already caught wild chickenpox in that five-year period.
Herpes zoster (shingles) most often occurs in the elderly and is only rarely seen in children. The incidence of herpes zoster in vaccinated adults is 0.9/1000 person-years, and is 0.33/1000 person-years in vaccinated children; this is lower than the overall incidence of 3.2–4.2/1000 person-years.
Adult shingles cases may increase after introduction of varicella vaccine, but evidence is unclear. While research using computer models has tended to support the hypothesis that vaccination programs would increase incidence of zoster in the short term, the evidence from epidemiological studies is mixed, and increases observed in zoster incidence in some studies may not be related to vaccination programs, as the incidence increases prior to the varicella vaccine program being initiated.
Regarding herpes zoster, the US Centers for Disease Control states:
"Chickenpox vaccines contain weakened live VZV, which may cause latent (dormant) infection. The vaccine-strain VZV can reactivate later in life and cause shingles. However, the risk of getting shingles from vaccine-strain VZV after chickenpox vaccination is much lower than getting shingles after natural infection with wild-type VZV." 
Rates of chickenpox
Prior to the introduction of the vaccine in 1995 in the USA (released in 1988 in Japan & Korea), there were around 4,000,000 cases per year in the US, mostly children, with typically 10,500–13,000 hospital admissions (range, 8,000–18,000), and 100–150 deaths each year. Though mostly children caught it, the majority of deaths (by as much as 80%) were among adults.
During 2003 and the first half of 2004, the US Centers for Disease Control and Prevention (CDC) reported eight deaths from varicella, six of whom were children or adolescents. These deaths and hospital admissions have substantially declined in the US due to vaccination, though the rate of shingles infection has increased as adults are less exposed to infected children (which would otherwise help protect against shingles). Ten years after the vaccine was recommended in the US, the CDC reported as much as a 90% drop in chicken pox cases, a varicella-related hospital admission decline of 71% and a 97% drop in chicken pox deaths among those under 20.
The Varicella Zoster vaccine is made from the Oka/Merck strain of live attenuated varicella virus. The virus was initially obtained from a child with natural varicella, introduced into human embryonic lung cell cultures, adapted to and propagated in embryonic guinea pig cell cultures, and finally propagated in human diploid cell cultures.
Japan was among the first countries to vaccinate for chickenpox. Routine vaccination against varicella zoster virus is also performed in the United States, and the incidence of chickenpox has been dramatically reduced there (from 4 million cases per year in the pre-vaccine era to approximately 400,000 cases per year as of 2005). In Europe most countries do not currently vaccinate against varicella, though the vaccine is gaining wider acceptance. Australia, Canada, and other countries have now adopted recommendations for routine immunization of children and susceptible adults against chickenpox.
Other countries, such as the United Kingdom, have targeted recommendations for the vaccine, e.g., for susceptible health care workers at risk of varicella exposure. In the UK, varicella antibodies are measured as part of the routine of prenatal care, and by 2005 all National Health Service personnel had determined their immunity and been immunized if they were non-immune and have direct patient contact. Population-based immunization against varicella is not otherwise practiced in the UK.
This vaccine is a shot given subcutaneously (under the skin). It is recommended for all children under 13 and for everyone 13 or older who has never had chickenpox.
Two doses are always recommended. In the first case a first dose is administered at 12 to 15 months and a second dose at age 4–6 years. For people older than 13 the two doses are administered 4 to 8 weeks apart.
The varicella vaccine is not recommended for seriously ill people, pregnant women, people who have experienced a serious allergic reaction to the varicella vaccine in the past, people who are allergic to gelatin, people allergic to neomycin, people suffering from an immune system disease, such as HIV, people receiving high doses of steroids, people receiving treatment for cancer with x-rays, drugs or chemotherapy, as well as people who have received blood products or transfusions during the past 5 months.
Serious side effects are very rare. From 1998 to 2013, only one vaccine-related death was reported: an English child with pre-existent leukemia. In some occasions, severe reactions have been reported such as meningitis and pneumonia (mainly in inadvertently vaccinated immunocompromised children) as well as anaphylaxis.
There is a short term risk of developing herpes zoster (shingles) following vaccination. However, this risk is less than the risk due to a natural infection resulting in chickenpox.:378 Most of the cases reported have been mild and have not been associated with serious complications.
Generally the vaccine is exceedingly safe: approximately 5% of children who receive the vaccine develop a fever or rash, but as of 1 May 2006[update], there have been no deaths yet attributable to the vaccine despite more than 40 million doses being administered. Cases of vaccine-related chickenpox have been reported in patients with a weakened immune system, but no deaths.
The literature contains several reports of adverse reactions following varicella vaccination, including vaccine-strain zoster in children and adults. A mean of 2,350 reports per year are attributed to varicella vaccine based on 20,004 cases reported to the Vaccine Adverse Event Reporting System (VAERS) database from May 1995 through December 2003. Minor events are known to be under-reported to VAERS.
A controversy has arisen because cell lines derived from aborted fetal tissue were used in its development, and thus violates the ethics and beliefs of people who oppose the use of aborted fetal tissue in medical research.
- "WHO Model List of EssentialMedicines". World Health Organization. October 2013. Retrieved 22 April 2014.
- "American Academy of Pediatrics. Committee on Infectious Diseases. Varicella vaccine update". Pediatrics 105 (1 Pt 1): 136–41. January 2000. doi:10.1542/peds.105.1.136. PMID 10617719.
- "Varicella Vaccine (Chickenpox)". Retrieved May 5, 2010.
- Goldman GS (2005). "Universal varicella vaccination: efficacy trends and effect on herpes zoster". Int J Toxicol 24 (4): 205–213. doi:10.1080/10915810591000659. PMID 16126614.
- Chaves SS, Gargiullo P, Zhang JX, et al. (March 2007). "Loss of vaccine-induced immunity to varicella over time". N. Engl. J. Med. 356 (11): 1121–9. doi:10.1056/NEJMoa064040. PMID 17360990.
- The Vaccines and other Biologicals department (May 2003). "Varicella vaccine". WHO. Archived from the original on 2006-08-13. Retrieved 2006-08-18. — which includes:
"Varicella vaccines: WHO position paper" (PDF). Weekly Epidemiological Record 73 (32): 241–248. 1998. PMID 9715106.
- "General questions about the disease". Varicella Disease (Chickenpox). CDCP. December 20, 2001. Retrieved 2006-08-18.
- Jack (2005). "Chickenpox Vaccine Linked with Shingles Epidemic". HerpesDoctor. Retrieved 2006-08-18.
- [dead link]
- Tugwell BD, Lee LE, Gillette H, Lorber EM, Hedberg K, Cieslak PR (March 2004). "Chickenpox outbreak in a highly vaccinated school population". Pediatrics 113 (3 Pt 1): 455–9. doi:10.1542/peds.113.3.455. PMID 14993534.
- "Chicken Pox Outbreak". Retrieved August 2014.
- By HealthiNation. "Yahoo! Health". Health.yahoo.com. Retrieved 2011-02-08.[dead link]
- Pirofski L, Casadevall A (1 January 1998). "Use of Licensed Vaccines for Active Immunization of the Immunocompromised Host". Clin Microbiol Rev 11 (1): 1–26. PMC 121373. PMID 9457426.
- Gershon, A. A. (2013). "Varicella zoster vaccines and their implications for development of HSV vaccines". Virology 435 (1): 29–36. doi:10.1016/j.virol.2012.10.006. PMC 3595154. PMID 23217613.
- Harpaz, Rafael. "Prevention of Herpes Zoster: Recommendations of the Advisory Committee on Immunization Practices (ACIP)". Centers for Disease Control. Retrieved 15 June 2014.
- Yih WK, Brooks DR, Lett SM, Jumaan AO, Zhang Z, Clements KM, Seward JF (2005). "The incidence of varicella and herpes zoster in Massachusetts as measured by the Behavioral Risk Factor Surveillance System (BRFSS) during a period of increasing varicella vaccine coverage, 1998–2003". BMC Public Health 5: 68–68. doi:10.1186/1471-2458-5-68. PMC 1177968. PMID 15960856.
- Brisson M, Gay NJ, Edmunds WJ, Andrews NJ (2002). "Exposure to varicella boosts immunity to Herpes-zoster: implications for mass vaccination against varicella". Vaccine 20 (19–20): 2500–7. doi:10.1016/S0264-410X(02)00180-9. PMID 12057605.
- Leung, Jessica; Rafael Harpaz, Noelle-Angelique Molinari, Aisha Jumaan, and Fangjun Zhou (2011-02-01). "Herpes Zoster Incidence Among Insured Persons in the United States, 1993–2006: Evaluation of Impact of Varicella Vaccination". Clinical Infectious Diseases 52 (3): 332–340. doi:10.1093/cid/ciq077.
- Tanuseputro, Peter; Brandon Zagorski; Kevin J. Chan; Jeffrey C. Kwong (2011-11-03). "Population-based incidence of herpes zoster after introduction of a publicly funded varicella vaccination program". Vaccine 29 (47): 8580–8584. doi:10.1016/j.vaccine.2011.09.024. PMID 21939721.
- Carville, Kylie; Michaela A. Riddell; Heath A. Kelly (2010-03-16). "A decline in varicella but an uncertain impact on zoster following varicella vaccination in Victoria, Australia". Vaccine 28 (13): 2532–2538. doi:10.1016/j.vaccine.2010.01.036. PMID 20117265.
- "Varicella (Chickenpox)". Center for Disease Control. Retrieved 16 April 2014.
- Lopez, Adriana; Schmid, Scott; Bialek, Stephanie (2011). "Chapter 17: Varicella". In Roush, Sandra W.; McIntyre, Lynne; Baldy, Linda M. Manual for the Surveillance of Vaccine-Preventable Diseases (5th ed.). Atlanta GA: Centers for Disease Control and Prevention.
- Seward JF, Watson BM, Peterson CL, et al. (2002). "Varicella disease after introduction of varicella vaccine in the United States, 1995–2000". JAMA 287 (5): 606–11. doi:10.1001/jama.287.5.606. PMID 11829699. Retrieved 2006-05-01.
- Nguyen HQ, Jumaan AO, Seward JF (2005). "Decline in mortality due to varicella after implementation of varicella vaccination in the United States" (PDF). N Engl J Med 352 (5): 450–8. doi:10.1056/NEJMoa042271. PMID 15689583. Retrieved 2006-05-01.
- Patel MS, Gebremariam A, Davis MM (2008). "Herpes zoster-related hospital admissons and expenditures before and after introduction of the varicella vaccine in the United States". Control Hosp. Epidemiol. 29 (12): 1157–1163. doi:10.1086/591975. PMID 18999945.
- Yih WK, Brooks DR, Lett SM, Jumaan AO, Zhang Z. Clements KM, Seward JF (2005). "The incidence of varicella and herpes zoster in Massachusetts as measured by the Behavioral Risk Factor Surveillance System (BRFSS) during a period of increasing varicella vaccine coverage, 1998–2003". BMC Public Health 5: 68–68. doi:10.1186/1471-2458-5-68. PMC 1177968. PMID 15960856.
- Yawn BP, Saddier P, Wollan PC, St Sauver JL, Kurland MJ, Sy LS (2007). "A Population-Based Study of the Incidence and Complication Rates of Herpes Zoster Before Zoster Vaccine Introduction". Mayo Clin Proc. 82 (11): 1341–1349. doi:10.4065/82.11.1341. PMID 17976353.
- Szabo, Liz (2011-07-25). "Vaccine has nearly eliminated chickenpox deaths in children". USA Today.
- "Who should get this vaccine?". Retrieved May 5, 2010.
- "Who should not receive the varicella vaccine?". Retrieved May 5, 2010.
- "What side effects have been reported with this vaccine?". Retrieved May 5, 2010.
- James, William D.; Berger, Timothy G.; et al. (2006). Andrews' Diseases of the Skin: clinical Dermatology. Saunders Elsevier. ISBN 0-7216-2921-0.
- "Vaccine Information for the public and health professionals". Retrieved May 5, 2010.
- Wise RP, Salive ME, Braun MM, et al. (2000). "Postlicensure safety surveillance for varicella vaccine". JAMA 284 (10): 1271–9. doi:10.1001/jama.284.10.1271. PMID 10979114.
- Quinlivan MA, Gershon AA, Nichols RA, La Russa P, Steinberg SP, Breuer J (2006). "Vaccine Oka Varicella-zoster virus genotypes are monomorphic in single vesicles and polymorphic in respiratory tract secretions". J Infect Dis 193 (7): 927–30. doi:10.1086/500835. PMID 16518753.
- For example:
- Wrensch M, Weinberg A, Wiencke J, Miike R, Barger G, Kelsey K (2001). "Prevalence of antibodies to four herpesviruses among adults with glioma and controls". Am J Epidem 154 (2): 161–5. doi:10.1093/aje/154.2.161. PMID 11447050.
- Naseri A, Good WV, Cunningham ET Jr (2003). "Herpes zoster virus sclerokeratitis and anterior uveitis in a child following varicella vaccination". Am J Ophthalmol 135 (3): 415–7. doi:10.1016/S0002-9394(02)01957-8. PMID 12614776.
- Schwab J, Ryan M (2004). "Varicella zoster virus meningitis in a previously immunized child". Pediatrics 114 (2): e273–4. doi:10.1542/peds.114.2.e273. PMID 15286270.
- Bronstein DE, Cotliar J, Votava-Smith JK, Powell MZ, Miller MJ, Cherry JD (2005). "Recurrent papular urticaria after varicella immunization in a 15-month-old girl". Pediatr Infect Dis J 24 (3): 269–70. doi:10.1097/01.inf.0000154330.47509.42. PMID 15750467.
- Binder NR, Holland GN, Hosea S, Silverberg ML (2005). "Herpes zoster ophthalmicus in an otherwise-healthy child". J Aapos 9 (6): 597–8. doi:10.1016/j.jaapos.2005.06.009. PMID 16414532.
- "NIP: Vacsafe/Concerns/Gen/Human Cell Cultures in Manufacturing Vaccines". Web.archive.org. Archived from the original on 2007-02-12. Retrieved 2011-02-08.
- Centers for Disease Control and Prevention (CDC) (March 2012). "FDA approval of an extended period for administering VariZIG for postexposure prophylaxis of varicella". MMWR Morb. Mortal. Wkly. Rep. 61 (12): 212. PMID 22456121.