Varicella vaccine#Side effects

Varicella vaccine is 70% to 90% effective for preventing varicella and more than 95% effective for preventing severe varicella.{{cite journal |vauthors=((Committee on Infectious Diseases)) |title=Prevention of varicella: recommendations for use of varicella vaccines in children, including a recommendation for a routine 2-dose varicella immunization schedule |journal=Pediatrics |volume=120 |issue=1 |pages=221–231 |date=July 2007 |pmid=17606582 |doi=10.1542/peds.2007-1089 |doi-access=free }} Follow-up evaluations have taken place in the United States of children immunized that revealed protection for at least 11 years. 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.{{Cite web |date=25 February 2021 |title=Chickenpox (Varicella) Vaccination |url=https://www.cdc.gov/vaccines/vpd/varicella/index.html |access-date=27 April 2022 |website=www.cdc.gov |language=en-us |archive-date=12 December 2018 |archive-url=https://web.archive.org/web/20181212000237/https://www.cdc.gov/vaccines/vpd/varicella/index.html |url-status=live }} 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 mild chickenpox also known as breakthrough disease.{{cite web|url=http://www.hoptechno.com/chickenpox-vac.htm|title=Varicella Vaccine (Chickenpox)|access-date=5 May 2010|url-status=live|archive-url=https://web.archive.org/web/20100315091845/http://www.hoptechno.com/chickenpox-vac.htm|archive-date=15 March 2010}}

Another vaccine, known as zoster vaccine, is simply a larger-than-normal dose of the same vaccine used against chickenpox and is used in older adults to reduce the risk of shingles (also called herpes zoster) and postherpetic neuralgia, which are caused by the same virus. The recombinant zoster (shingles) vaccine is recommended for adults aged 50 years and older.{{cite web | title=Recombinant Shingles VIS | website=U.S. Centers for Disease Control and Prevention (CDC) | date=February 2022 | url=https://www.cdc.gov/vaccines/hcp/vis/vis-statements/shingles-recombinant.html | archive-url=https://web.archive.org/web/20191023003610/https://www.cdc.gov/vaccines/hcp/vis/vis-statements/shingles-recombinant.html | archive-date=23 October 2019 | url-status=live | access-date=22 October 2019}}

The long-term duration of protection from varicella vaccine is unknown, but there are now persons vaccinated twenty years ago with no evidence of waning immunity, while others have become vulnerable in as few as six years. Assessments of the duration of immunity are complicated in an environment where natural disease is still common, which typically leads to an overestimation of effectiveness.{{cite journal | vauthors = Goldman GS | title = Universal varicella vaccination: efficacy trends and effect on herpes zoster | journal = International Journal of Toxicology | volume = 24 | issue = 4 | pages = 205–213 | year = 2005 | pmid = 16126614 | doi = 10.1080/10915810591000659 | citeseerx = 10.1.1.540.9230 | s2cid = 34310228 }}

Some vaccinated children have been found to lose their protective antibodies in as little as five to eight years.{{cite journal | vauthors = Chaves SS, Gargiullo P, Zhang JX, Civen R, Guris D, Mascola L, Seward JF | title = Loss of vaccine-induced immunity to varicella over time | journal = The New England Journal of Medicine | volume = 356 | issue = 11 | pages = 1121–1129 | date = March 2007 | pmid = 17360990 | doi = 10.1056/NEJMoa064040 | doi-access = free }} However, according to the World Health Organization (WHO): "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. As time goes on, boosters may be necessary. Persons exposed to the virus after vaccination tend to experience milder cases of chickenpox if they develop the disease.{{cite web | work=Varicella Disease (Chickenpox) | title=General questions about the disease | url=https://www.cdc.gov/nip/diseases/varicella/faqs-gen-disease.htm | date=20 December 2001 | publisher=CDCP | access-date=18 August 2006 | url-status=dead | archive-url=https://web.archive.org/web/20060825124430/http://www.cdc.gov/nip/diseases/varicella/faqs-gen-disease.htm | archive-date=25 August 2006 }}

File:1990-2001 Cases of Varicella in the U.S..jpg

Prior to the widespread introduction of the vaccine in the United States in 1995 (1986 in Japan and 1988 in Korea{{cite journal | vauthors = Takahashi M | title = 25 years' experience with the Biken Oka strain varicella vaccine: a clinical overview | journal = Paediatric Drugs | volume = 3 | issue = 4 | pages = 285–292 | date = 2001 | pmid = 11354700 | doi = 10.2165/00128072-200103040-00005 | s2cid = 25328919 }}), there were around 4,000,000 cases per year in the United States, mostly in children, with typically 10,500–13,000 hospital admissions (range, 8,000–18,000), and 100–150 deaths each year.{{cite web | author=The Vaccines and other Biologicals department | publisher=World Health Organization (WHO) | title=Varicella vaccine | url=https://www.who.int/vaccines/en/varicella.shtml | date=May 2003 | access-date=18 August 2006 | archive-url=https://web.archive.org/web/20060813125255/http://www.who.int/vaccines/en/varicella.shtml | archive-date=13 August 2006 | url-status=dead }}{{cite book | vauthors = Lopez A, Schmid S, Bialek S |chapter=Chapter 17: Varicella |chapter-url=https://www.cdc.gov/vaccines/pubs/surv-manual/chpt17-varicella.html | veditors = Roush SW, McIntyre L, Baldy LM | title=Manual for the surveillance of vaccine-preventable diseases |publisher=Centers for Disease Control and Prevention (CDC) |location=Atlanta GA |year=2011 |edition=5th |url=https://www.cdc.gov/vaccines/pubs/surv-manual/index.html |url-status=live |archive-url=https://web.archive.org/web/20120425224442/http://www.cdc.gov/vaccines/pubs/surv-manual/index.html |archive-date=25 April 2012 }} Most of the deaths were among young children.{{cite news |vauthors=Altman L |title=After Long Debate, Vaccine For Chicken Pox Is Approved |url=https://www.nytimes.com/1995/03/18/us/after-long-debate-vaccine-for-chicken-pox-is-approved.html |work=New York Times |date=18 March 1995 |quote=Up to 100 deaths occur from chicken pox each year, and most of the victims are young children. |access-date=29 September 2021 |archive-date=29 September 2021 |archive-url=https://web.archive.org/web/20210929214144/https://www.nytimes.com/1995/03/18/us/after-long-debate-vaccine-for-chicken-pox-is-approved.html |url-status=live }}

During 2003, and the first half of 2004, the 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,{{cite journal | vauthors = Seward JF, Watson BM, Peterson CL, Mascola L, Pelosi JW, Zhang JX, Maupin TJ, Goldman GS, Tabony LJ, Brodovicz KG, Jumaan AO, Wharton M | display-authors = 6 | title = Varicella disease after introduction of varicella vaccine in the United States, 1995–2000 | journal = JAMA | volume = 287 | issue = 5 | pages = 606–611 | date = February 2002 | pmid = 11829699 | doi = 10.1001/jama.287.5.606 | doi-access = free }}{{cite journal | vauthors = Nguyen HQ, Jumaan AO, Seward JF | title = Decline in mortality due to varicella after implementation of varicella vaccination in the United States | journal = The New England Journal of Medicine | volume = 352 | issue = 5 | pages = 450–458 | date = February 2005 | pmid = 15689583 | doi = 10.1056/NEJMoa042271 | doi-access = free }} though the rate of shingles infection has increased as adults are less exposed to infected children (which would otherwise help protect against shingles).{{cite journal | vauthors = Patel MS, Gebremariam A, Davis MM | title = Herpes zoster-related hospitalizations and expenditures before and after introduction of the varicella vaccine in the United States | journal = Infection Control and Hospital Epidemiology | volume = 29 | issue = 12 | pages = 1157–1163 | date = December 2008 | pmid = 18999945 | doi = 10.1086/591975 | s2cid = 21934553 }}{{cite journal | vauthors = Yih WK, Brooks DR, Lett SM, Jumaan AO, Zhang Z, Clements KM, Seward JF | title = 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 | journal = BMC Public Health | volume = 5 | pages = 68 | date = June 2005 | pmid = 15960856 | pmc = 1177968 | doi = 10.1186/1471-2458-5-68 | doi-access = free }}{{cite journal | vauthors = Yawn BP, Saddier P, Wollan PC, St Sauver JL, Kurland MJ, Sy LS | title = A population-based study of the incidence and complication rates of herpes zoster before zoster vaccine introduction | journal = Mayo Clinic Proceedings | volume = 82 | issue = 11 | pages = 1341–1349 | date = November 2007 | pmid = 17976353 | doi = 10.4065/82.11.1341 }} Ten years after the vaccine was recommended in the US, the CDC reported as much as a 90% drop in chickenpox cases, a varicella-related hospital admission decline of 71% and a 97% drop in chickenpox deaths among those under 20.{{cite news| vauthors =Szabo L |title=Vaccine has nearly eliminated chickenpox deaths in children|newspaper=USA Today|date=25 July 2011|url=http://yourlife.usatoday.com/health/medical/pediatrics/story/2011/07/Vaccine-has-nearly-eliminated-chickenpox-deaths-in-children/49642072/1|url-status=dead|archive-url=https://web.archive.org/web/20110926045309/http://yourlife.usatoday.com/health/medical/pediatrics/story/2011/07/Vaccine-has-nearly-eliminated-chickenpox-deaths-in-children/49642072/1|archive-date=26 September 2011|access-date=15 November 2011}}

Vaccines are less effective among high-risk patients, as well as being more dangerous because they contain attenuated live viruses. 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 those five years.{{cite journal | vauthors = Pirofski LA, Casadevall A | title = Use of licensed vaccines for active immunization of the immunocompromised host | journal = Clinical Microbiology Reviews | volume = 11 | issue = 1 | pages = 1–26 | date = January 1998 | pmid = 9457426 | pmc = 121373 | doi = 10.1128/CMR.11.1.1 }}

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.{{cite journal | vauthors = Harpaz R, Ortega-Sanchez IR, Seward JF | title = Prevention of herpes zoster: recommendations of the Advisory Committee on Immunization Practices (ACIP) | journal = MMWR. Recommendations and Reports | volume = 57 | issue = RR-5 | pages = 1–30; quiz CE2–4 | date = June 2008 | pmid = 18528318 | url = https://www.cdc.gov/mmwr/PDF/rr/rr5705.pdf | access-date = 9 October 2020 | archive-date = 8 June 2021 | archive-url = https://web.archive.org/web/20210608232821/http://www.cdc.gov/mmwr/pdf/rr/rr5705.pdf | url-status = live }}

The risk of developing shingles is reduced for children who receive the varicella vaccine, but not eliminated. The CDC stated in 2014: "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."{{cite web|title=CDC – Varicella Vaccine – Vaccine Safety|website=Centers for Disease Control and Prevention (CDC)|url=http://www.cdc.gov/vaccinesafety/vaccines/varicella/|archive-url=https://web.archive.org/web/20150825030946/http://www.cdc.gov/vaccinesafety/vaccines/varicella/|archive-date=25 August 2015}}

The risk of shingles is significantly lower among children who have received varicella vaccination, including those who are immunocompromised. The risk of shingles is approximately 80% lower among healthy vaccinated children compared to unvaccinated children who had wild-type varicella.{{Cite web |date=2022-10-21 |title=Chickenpox (Varicella) for Healthcare Professionals |url=https://www.cdc.gov/chickenpox/hcp/index.html |access-date=2023-03-08 |website=Centers for Disease Control and Prevention |language=en-us |archive-date=6 December 2011 |archive-url=https://web.archive.org/web/20111206225423/http://www.cdc.gov/chickenpox/hcp/index.html |url-status=live }}{{Cite web |vauthors=Haelle T |title=Two-for-One: Chickenpox Vaccine Lowers Shingles Risk in Children - Immunization reduces the likelihood of a painful reemergence of the virus in kids |url=https://www.scientificamerican.com/article/two-for-one-chickenpox-vaccine-lowers-shingles-risk-in-children/ |access-date=2023-03-08 |website=Scientific American |date=October 2019 |language=en |archive-date=20 February 2020 |archive-url=https://web.archive.org/web/20200220025048/https://www.scientificamerican.com/article/two-for-one-chickenpox-vaccine-lowers-shingles-risk-in-children/ |url-status=live }} A population with high varicella vaccination also has lower incidence of shingles in unvaccinated children, due to herd immunity.

The WHO recommends one or two doses with the initial dose given at 12 to 18 months of age. The second dose, if given, should occur at least one to three months later. The second dose, if given, provides the additional benefit of improved protection against all varicella.{{cite journal | vauthors = Marin M, Marti M, Kambhampati A, Jeram SM, Seward JF | title = Global Varicella Vaccine Effectiveness: A Meta-analysis | journal = Pediatrics | volume = 137 | issue = 3 | pages = e20153741 | date = March 2016 | pmid = 26908671 | doi = 10.1542/peds.2015-3741 | doi-access = free }} 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.{{cite web|url=https://www.cdc.gov/vaccines/vpd/varicella/public/index.html|title=Chickenpox Vaccination: What Everyone Should Know|access-date=26 October 2021|date=7 August 2019|work=Centers for Disease Control and Prevention (CDC)|archive-date=22 October 2021|archive-url=https://web.archive.org/web/20211022140517/https://www.cdc.gov/vaccines/vpd/varicella/public/index.html|url-status=live}}

In the United States, two doses are recommended by the CDC. For a routine vaccination, the first dose is administered at 12 to 15 months of age and the second dose at age 4–6 years. However, the second dose can be given as early as 3 months after the first dose. If an individual misses the timing for the routine vaccination, the individual is eligible to receive a catch-up vaccination. For a catch-up vaccination, individuals between 7 and 12 years old should receive a two-dose series 3 months apart (a minimum interval of 4 weeks). For individuals 13–18 years old, the catch-up vaccination should be given 4 to 8 weeks apart (a minimum interval of 4 weeks).{{Cite web|url=https://www.cdc.gov/vaccines/schedules/hcp/imz/child-adolescent.html|title=Recommended Child and Adolescent Immunization Schedule for ages 18 years or younger, United States, 2019|date=5 February 2019|website=Centers for Disease Control and Prevention (CDC)|access-date=2 August 2019|archive-date=6 March 2016|archive-url=https://web.archive.org/web/20160306220930/http://www.cdc.gov/vaccines/schedules/hcp/imz/child-adolescent.html|url-status=live}} The varicella vaccine did not become widely available in the United States until 1995.{{cite web |url=https://www.cdc.gov/chickenpox/surveillance/monitoring-varicella.html |title=Monitoring the Impact of Varicella Vaccination |publisher=Centers for Disease Control and Prevention (CDC) |date=1 July 2016 |access-date=14 July 2017 |url-status=live |archive-url=https://web.archive.org/web/20170617201344/https://www.cdc.gov/chickenpox/surveillance/monitoring-varicella.html |archive-date=17 June 2017 }}

In the UK, the vaccine is only available on the National Health Service for those who are in close contact with someone who is particularly vulnerable to chickenpox.{{cite web |title=Chickenpox vaccine FAQs |url=https://www.nhs.uk/conditions/vaccinations/chickenpox-vaccine-questions-answers/ |website=NHS website for England |date=31 July 2019 |access-date=4 July 2022 |archive-date=12 April 2020 |archive-url=https://web.archive.org/web/20200412144833/https://www.nhs.uk/conditions/vaccinations/chickenpox-vaccine-questions-answers/ |url-status=live }} As there is an increased risk of shingles in adults due to possible lack of contact with chickenpox-infected children providing a natural boosting to immunity, and the fact that chickenpox is usually a mild illness, the NHS cites concerns about unvaccinated children catching chickenpox as adults when it is more dangerous. However, the vaccine is approved for 12 months and up and is available privately, with a second dose to be given a year after the first.

The varicella vaccine is not recommended for seriously ill people, pregnant women, people who have tuberculosis, 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 receiving high doses of steroids, people receiving treatment for cancer with x-rays or chemotherapy, as well as people who have received blood products or transfusions during the past five months.{{cite web|url=http://familydoctor.org/online/famdocen/home/healthy/vaccines/193.html|title=Who should not receive the varicella vaccine?|access-date=5 May 2010|url-status=live|archive-url=https://web.archive.org/web/20100615082157/http://familydoctor.org/online/famdocen/home/healthy/vaccines/193.html|archive-date=15 June 2010}}{{Cite web |date=15 August 2019 |title=Chickenpox VIS |url=https://www.cdc.gov/vaccines/hcp/vis/vis-statements/varicella.html |archive-url=https://web.archive.org/web/20190507145832/https://www.cdc.gov/vaccines/hcp/vis/vis-statements/varicella.html |archive-date=7 May 2019 |access-date=3 March 2023 |website=Centers for Disease Control and Prevention (CDC)}} Additionally, the varicella vaccine is not recommended for people who are taking salicylates (e.g. aspirin). After receiving the varicella vaccine, the use of salicylates should be avoided for at least six weeks. The varicella vaccine is also not recommended for individuals who have received a live vaccine in the last four weeks, because live vaccines that are administered too soon within one another may not be as effective. It may be usable in people with HIV infections who have a good blood count and are receiving appropriate treatment. Specific antiviral medication, such as acyclovir, famciclovir, or valacyclovir, are not recommended 24 hours before and 14 days after vaccination.{{cite web |title=General Best Practice Guidelines for Immunization: Contraindications and Precautions |url=https://www.cdc.gov/vaccines/hcp/acip-recs/general-recs/contraindications.pdf |access-date=29 January 2019 |archive-date=29 January 2019 |archive-url=https://web.archive.org/web/20190129064042/https://www.cdc.gov/vaccines/hcp/acip-recs/general-recs/contraindications.pdf |url-status=live }}

Serious side effects are very rare. From 1998 to 2013, only one vaccine-related death was reported: an English child with pre-existent leukemia. On some occasions, severe reactions such as meningitis and pneumonia have been reported (mainly in inadvertently vaccinated immunocompromised children) as well as anaphylaxis.{{cite journal | vauthors = Gershon AA | title = Varicella zoster vaccines and their implications for development of HSV vaccines | journal = Virology | volume = 435 | issue = 1 | pages = 29–36 | date = January 2013 | pmid = 23217613 | pmc = 3595154 | doi = 10.1016/j.virol.2012.10.006 }}

The possible mild side effects include redness, stiffness, and soreness at the injection site, as well as fever. A few people may develop a mild rash, which usually appears around the injection site.{{cite web|url=http://www.vaccineinformation.org/varicel/qandavax.asp|title=What side effects have been reported with this vaccine?|access-date=5 May 2010|url-status=live|archive-url=https://web.archive.org/web/20100504200810/http://www.vaccineinformation.org/varicel/qandavax.asp|archive-date=4 May 2010}}

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.{{cite book | vauthors = James WD, Berger TG |title=Andrews' Diseases of the Skin: clinical Dermatology |publisher=Saunders Elsevier |year=2006 |isbn=978-0721629216 |display-authors=etal}}{{rp|378}} Most of the cases reported have been mild and have not been associated with serious complications.{{cite web| url= http://www.vaccineinformation.org/varicel/qandavax.asp |title=Vaccine Information for the public and health professionals|access-date=5 May 2010|url-status=live|archive-url= https://web.archive.org/web/20100504200810/http://www.vaccineinformation.org/varicel/qandavax.asp |archive-date=4 May 2010 }}

Approximately 5% of children who receive the vaccine develop a fever or rash. Adverse reaction reports for the period 1995 to 2005 found no deaths attributed to the vaccine despite approximately 55.7 million doses being delivered.{{cite journal | vauthors = Galea SA, Sweet A, Beninger P, Steinberg SP, Larussa PS, Gershon AA, Sharrar RG | title = The safety profile of varicella vaccine: a 10-year review | journal = The Journal of Infectious Diseases | volume = 197 | issue = Supplement 2 | pages = S165–S169 | date = March 2008 | pmid = 18419392 | doi = 10.1086/522125 | hdl = 2027.42/61293 | s2cid = 25145408 | hdl-access = free }} Cases of vaccine-related chickenpox have been reported in patients with a weakened immune system,{{cite journal | vauthors = Wise RP, Salive ME, Braun MM, Mootrey GT, Seward JF, Rider LG, Krause PR | title = Postlicensure safety surveillance for varicella vaccine | journal = JAMA | volume = 284 | issue = 10 | pages = 1271–1279 | date = September 2000 | pmid = 10979114 | doi = 10.1001/jama.284.10.1271 | doi-access = free }}{{cite journal | vauthors = Quinlivan MA, Gershon AA, Nichols RA, La Russa P, Steinberg SP, Breuer J | title = Vaccine Oka varicella-zoster virus genotypes are monomorphic in single vesicles and polymorphic in respiratory tract secretions | journal = The Journal of Infectious Diseases | volume = 193 | issue = 7 | pages = 927–930 | date = April 2006 | pmid = 16518753 | doi = 10.1086/500835 | doi-access = free }} but no deaths.

The literature contains several reports of adverse reactions following varicella vaccination, including vaccine-strain zoster in children and adults.For example:

• {{cite journal | vauthors = Wrensch M, Weinberg A, Wiencke J, Miike R, Barger G, Kelsey K | title = Prevalence of antibodies to four herpesviruses among adults with glioma and controls | journal = American Journal of Epidemiology | volume = 154 | issue = 2 | pages = 161–165 | date = July 2001 | pmid = 11447050 | doi = 10.1093/aje/154.2.161 | doi-access = free }}
• {{cite journal | vauthors = Naseri A, Good WV, Cunningham ET | title = Herpes zoster virus sclerokeratitis and anterior uveitis in a child following varicella vaccination | journal = American Journal of Ophthalmology | volume = 135 | issue = 3 | pages = 415–417 | date = March 2003 | pmid = 12614776 | doi = 10.1016/S0002-9394(02)01957-8 }}
• {{cite journal | vauthors = Schwab J, Ryan M | title = Varicella zoster virus meningitis in a previously immunized child | journal = Pediatrics | volume = 114 | issue = 2 | pages = e273–e274 | date = August 2004 | pmid = 15286270 | doi = 10.1542/peds.114.2.e273 | doi-access = free }}
• {{cite journal | vauthors = Bronstein DE, Cotliar J, Votava-Smith JK, Powell MZ, Miller MJ, Cherry JD | title = Recurrent papular urticaria after varicella immunization in a fifteen-month-old girl | journal = The Pediatric Infectious Disease Journal | volume = 24 | issue = 3 | pages = 269–270 | date = March 2005 | pmid = 15750467 | doi = 10.1097/01.inf.0000154330.47509.42 | doi-access = free }}
• {{cite journal | vauthors = Binder NR, Holland GN, Hosea S, Silverberg ML | title = Herpes zoster ophthalmicus in an otherwise-healthy child | journal = Journal of AAPOS | volume = 9 | issue = 6 | pages = 597–598 | date = December 2005 | pmid = 16414532 | doi = 10.1016/j.jaapos.2005.06.009 }}

The varicella-zoster vaccine is made from the Oka/Merck strain of live attenuated varicella virus. The Oka 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 a human diploid cell line originally derived from fetal tissues (WI-38).{{cite web | title=Varivax | website=U.S. Food and Drug Administration (FDA) | date=16 September 2020 | url=https://www.fda.gov/vaccines-blood-biologics/vaccines/varivax | access-date=27 February 2021 | archive-date=7 March 2021 | archive-url=https://web.archive.org/web/20210307154652/https://www.fda.gov/vaccines-blood-biologics/vaccines/varivax | url-status=live }}{{Cite web |date=22 July 2017 |title=Varivax |url=https://www.fda.gov/vaccines-blood-biologics/vaccines/varivax-refrigerated-and-frozen-formulations |url-status=live |archive-url=https://wayback.archive-it.org/7993/20170722071820/https://www.fda.gov/BiologicsBloodVaccines/Vaccines/ApprovedProducts/ucm094073.htm |archive-date=22 July 2017 |access-date=8 March 2023 |website=U.S. Food and Drug Administration (FDA)}} Takahashi and his colleagues used the Oka strain to develop a live attenuated varicella vaccine in Japan in the early 1970s. This strain was further developed by pharmaceutical companies such as Merck & Co. and GlaxoSmithKline.{{cite journal | vauthors = Tillieux SL, Halsey WS, Thomas ES, Voycik JJ, Sathe GM, Vassilev V | title = Complete DNA sequences of two oka strain varicella-zoster virus genomes | journal = Journal of Virology | volume = 82 | issue = 22 | pages = 11023–11044 | date = November 2008 | pmid = 18787000 | pmc = 2573284 | doi = 10.1128/JVI.00777-08 }} American vaccinologist Maurice Hilleman's team at Merck then used the Oka strain to prepare a chickenpox vaccine in 1981.{{cite journal | vauthors = Schillie S, Vellozzi C, Reingold A, Harris A, Haber P, Ward JW, Nelson NP | title = Prevention of Hepatitis B Virus Infection in the United States: Recommendations of the Advisory Committee on Immunization Practices | journal = MMWR. Recommendations and Reports | volume = 67 | issue = 1 | pages = 443–470 | date = January 2018 | pmc = 7150172 | doi = 10.1016/B978-0-12-804571-8.00003-2 | pmid = 29939980 | isbn = 9780128045718 }}{{Cite web|title=Chickenpox (Varicella) |url=https://www.historyofvaccines.org/content/articles/chickenpox-varicella|access-date=6 February 2021|website=History of Vaccines |archive-date=22 January 2021|archive-url=https://web.archive.org/web/20210122165132/https://www.historyofvaccines.org/content/articles/chickenpox-varicella|url-status=live}}{{Cite web|title=Maurice Ralph Hilleman (1919–2005) |url=https://embryo.asu.edu/pages/maurice-ralph-hilleman-1919-2005|access-date=6 February 2021|website=The Embryo Project Encyclopedia|archive-date=27 August 2017|archive-url=https://web.archive.org/web/20170827180232/https://embryo.asu.edu/pages/maurice-ralph-hilleman-1919-2005|url-status=live}}

Japan was among the first countries to vaccinate for chickenpox. The vaccine developed by Hilleman was first licensed in the United States in 1995.{{Cite web|url=http://www.immunize.org/catg.d/p4202.pdf|title=Varicella (chickenpox): Questions and Answers|access-date=23 April 2023|archive-date=2 October 2018|archive-url=https://web.archive.org/web/20181002020113/http://www.immunize.org/catg.d/p4202.pdf|url-status=live}} Routine vaccination against varicella zoster virus is also performed in the United States, and the incidence of chickenpox has been dramatically reduced there (from four million cases per year in the pre-vaccine era to approximately 390,000 cases per year {{as of|2014|lc=yes}}).{{cite journal | vauthors = Lopez AS, Zhang J, Marin M | title = Epidemiology of Varicella During the 2-Dose Varicella Vaccination Program - United States, 2005-2014 | journal = MMWR. Morbidity and Mortality Weekly Report | volume = 65 | issue = 34 | pages = 902–905 | date = September 2016 | pmid = 27584717 | doi = 10.15585/mmwr.mm6534a4 | doi-access = free }}

{{as of|2019|lc=n}}, standalone varicella vaccines are available in all 27 European Union member countries, and 16 countries also offer a combined measles, mumps, rubella, and varicella vaccine (MMRV).{{cite journal | vauthors = Spoulou V, Alain S, Gabutti G, Giaquinto C, Liese J, Martinon-Torres F, Vesikari T | title = Implementing Universal Varicella Vaccination in Europe: The Path Forward | journal = The Pediatric Infectious Disease Journal | volume = 38 | issue = 2 | pages = 181–188 | date = February 2019 | pmid = 30408002 | doi = 10.1097/INF.0000000000002233 | s2cid = 53239234 | hdl = 11392/2400466 | hdl-access = free }} Twelve European countries (Austria, Andorra, Cyprus, Czech Republic, Finland, Germany, Greece, Hungary, Italy, Latvia, Luxembourg and Spain) have universal varicella vaccination (UVV) policies, though only six of these countries have made it available at no cost via government funding. EU member states that have not implemented UVV cite reasons such as "a perceived low disease burden and low public health priority," the cost and cost-effectiveness, the possible risk of herpes zoster when vaccinating older adults, and rare fevers leading to seizures after the first dose of the MMRV vaccine. "Countries that implemented UVV experienced decreases in varicella incidence, hospitalizations, and complications, showing overall beneficial impact."

Varicella vaccination is recommended in Canada for all healthy children aged 1 to 12, as well as susceptible adolescents and adults 50 years of age and younger; "may be considered for people with select immunodeficiency disorders; and "should be prioritized" for susceptible individuals, including "non-pregnant women of childbearing age, household contacts of immunocompromised individuals, members of a household expecting a newborn, health care workers, adults who may be exposed occupationally to varicella (for example, people who work with young children), immigrants and refugees from tropical regions, people receiving chronic salicylate therapy (for example, acetylsalicylic acid [ASA])," and others.{{cite web |title=Varicella (chickenpox) vaccine: Canadian Immunization Guide For health professionals |url=https://www.canada.ca/en/public-health/services/publications/healthy-living/canadian-immunization-guide-part-4-active-vaccines/page-24-varicella-chickenpox-vaccine.html |website=Canadian Immunization Guide |publisher=Health Canada |access-date=3 October 2021 |date=July 2018 |archive-date=21 September 2021 |archive-url=https://web.archive.org/web/20210921072359/https://www.canada.ca/en/public-health/services/publications/healthy-living/canadian-immunization-guide-part-4-active-vaccines/page-24-varicella-chickenpox-vaccine.html |url-status=live }}

Australia has adopted recommendations for routine immunization of children and susceptible adults against chickenpox.{{cite web |date=15 April 2021 |title=Chickenpox immunisation service (Link invalid) |url=https://www.health.gov.au/health-topics/immunisation/immunisation-services/chickenpox-immunisation-service-0 |access-date=26 October 2021 |website=health.gov.au |archive-date=26 October 2021 |archive-url=https://web.archive.org/web/20211026102615/https://www.health.gov.au/health-topics/immunisation/immunisation-services/chickenpox-immunisation-service-0 |url-status=live }}

Other countries, such as the United Kingdom, have targeted recommendations for the vaccine, e.g., for susceptible healthcare 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 had direct patient contact. Population-based immunization against varicella is not otherwise practised in the UK.{{cite web |url=https://www.nhs.uk/conditions/vaccinations/chickenpox-vaccine-questions-answers/ |title=Chickenpox vaccine FAQs |website=NHS.uk |date=31 July 2019 |access-date=1 April 2020 |archive-date=12 April 2020 |archive-url=https://web.archive.org/web/20200412144833/https://www.nhs.uk/conditions/vaccinations/chickenpox-vaccine-questions-answers/ |url-status=live }}

Since 2013, the MMRV vaccine has been offered for free to all Brazilian citizens.{{cite journal | vauthors = Scotta MC, Paternina-de la Ossa R, Lumertz MS, Jones MH, Mattiello R, Pinto LA | title = Early impact of universal varicella vaccination on childhood varicella and herpes zoster hospitalizations in Brazil | journal = Vaccine | volume = 36 | issue = 2 | pages = 280–284 | date = January 2018 | pmid = 29198917 | doi = 10.1016/j.vaccine.2017.11.057 }}

{{Main|Use of fetal tissue in vaccine development#Position of the Catholic Church}}

The use of fetal tissue in vaccine development is the practice of researching, developing, and producing vaccines through growing viruses in cultured (laboratory-grown) cells that were originally derived from human fetal tissue. Since the cell strains in use originate from abortions, there has been some opposition to the practice and the resulting vaccines on religious and moral grounds.

The Roman Catholic Church is opposed to abortion. Nevertheless, the Pontifical Academy for Life stated in 2017 that "clinically recommended vaccinations can be used with a clear conscience and that the use of such vaccines does not signify some sort of cooperation with voluntary abortion".{{Cite web|title=Note on Italian vaccine issue|url=http://www.academyforlife.va/content/pav/en/the-academy/activity-academy/note-vaccini.html|access-date=3 October 2021|website=www.academyforlife.va|language=en|archive-date=21 February 2023|archive-url=https://web.archive.org/web/20230221091534/https://www.academyforlife.va/content/pav/en/the-academy/activity-academy/note-vaccini.html|url-status=dead}} On 21 December 2020, the Vatican's doctrinal office, the Congregation for the Doctrine of the Faith, further clarified that it is "morally {{linktext|licit}}" for Catholics to receive vaccines derived from fetal cell lines or in which such lines were used in testing or development, because "passive material cooperation in the procured abortion from which these cell lines originate is, on the part of those making use of the resulting vaccines, remote" and "does not and should not in any way imply that there is a moral endorsement of the use of cell lines proceeding from aborted fetuses".{{cite journal |author1=Congregation for the Doctrine of the Faith |title=Note of the Congregation for the Doctrine of the Faith on the morality of using some anti-Covid-19 vaccines, 21.12.2020 |journal=Summary of Bulletin, Holy See Press Office |date=21 December 2020 |url=https://press.vatican.va/content/salastampa/en/bollettino/pubblico/2020/12/21/201221c.html |publisher=Holy See |access-date=3 October 2021 |archive-date=3 October 2021 |archive-url=https://web.archive.org/web/20211003173925/https://press.vatican.va/content/salastampa/en/bollettino/pubblico/2020/12/21/201221c.html |url-status=live }}

{{Reflist}}

• {{cite book | vauthors = ((World Health Organization)) | title = The immunological basis for immunization series : Module 10: Varicella-zoster virus | publisher = World Health Organization (WHO) | date = May 2008 | hdl = 10665/43906 | isbn = 978-9241596770 | hdl-access=free }}
• {{cite book | title=Immunisation against infectious disease | chapter=Chapter 34: Varicella | chapter-url=https://www.gov.uk/government/publications/varicella-the-green-book-chapter-34 | publisher=Public Health England | veditors = Ramsay M | url=https://www.gov.uk/government/collections/immunisation-against-infectious-disease-the-green-book | date=March 2013 }}
• {{cite book | publisher = U.S. Centers for Disease Control and Prevention (CDC) | title = Epidemiology and Prevention of Vaccine-Preventable Diseases | veditors = Hall E, Wodi AP, Hamborsky J, Morelli V, Schillie S | edition = 14th | location = Washington D.C. | year = 2021 | chapter = Chapter 22: Varicella | chapter-url = https://www.cdc.gov/vaccines/pubs/pinkbook/varicella.html | url=https://www.cdc.gov/vaccines/pubs/pinkbook/index.html }}`
• {{cite book | name-list-style = vanc | chapter = Chapter 17: Varicella | chapter-url = https://www.cdc.gov/vaccines/pubs/surv-manual/chpt17-varicella.html | veditors = Roush SW, Baldy LM, Hall MA | title = Manual for the surveillance of vaccine-preventable diseases | publisher = Centers for Disease Control and Prevention (CDC) | location = Atlanta GA | url = https://www.cdc.gov/vaccines/pubs/surv-manual/ | date = 9 January 2020 }}

• {{cite web | title=Chickenpox Vaccine Information Statement | website=U.S. Centers for Disease Control and Prevention (CDC)| date=10 August 2021| url=https://www.cdc.gov/vaccines/hcp/vis/vis-statements/varicella.html }}
• {{cite web | title=Chickenpox (Varicella) Vaccination | website=U.S. Centers for Disease Control and Prevention (CDC) | date=25 February 2021 | url=https://www.cdc.gov/vaccines/vpd/varicella/ }}
• {{MeshName|Chickenpox Vaccine}}

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