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{{Short description|Vaccine to prevent chickenpox}}
{{tooshort|date=September 2009}}
{{Distinguish|Variola vaccine}}
{{Use dmy dates|date=November 2022}}
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| caption = Varicella vaccine
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<!-- Definition and medical uses -->
'''Varicella vaccine''', also known as '''chickenpox vaccine''', is a ] that protects against ].<ref name=CDC2015>{{cite web|title=Chickenpox (Varicella) Vaccine Safety|url=https://www.cdc.gov/vaccinesafety/vaccines/varicella-vaccine.html|website=] (CDC) |access-date=15 December 2015|date=27 October 2015|url-status=live|archive-url=https://web.archive.org/web/20151222083733/http://www.cdc.gov/vaccinesafety/vaccines/varicella-vaccine.html|archive-date=22 December 2015}}</ref> One dose of vaccine prevents 95% of moderate disease and 100% of severe disease.<ref name=WHO2014/> Two doses of vaccine are more effective than one.<ref name=WHO2014/> If given to those who are not immune within five days of exposure to chickenpox it prevents most cases of the disease.<ref name=WHO2014/> Vaccinating a large portion of the population also protects those who are not vaccinated.<ref name=WHO2014/> It is given by ].<ref name=WHO2014/> Another vaccine, known as ], is used to prevent diseases caused by the same virus – the ].<ref name="zostavax-cdc">{{cite web|url=https://www.cdc.gov/vaccines/vpd/shingles/hcp/zostavax/hcp-vax-recs.html|title=Herpes Zoster Vaccination|work=Centers for Disease Control and Prevention|access-date=26 October 2021|date=31 July 2015|archive-date=26 October 2021|archive-url=https://web.archive.org/web/20211026095854/https://www.cdc.gov/vaccines/vpd/shingles/hcp/zostavax/hcp-vax-recs.html|url-status=live}}</ref>


<!-- Recommendations -->
The '''varicella vaccine''' is a ] that protects against the viral disease commonly known as ] caused by ] (VZV). Varicella vaccine is marketed as '''Varivax''' in the U.S. by ]. Another vaccine that is known as ''']''' and used to reduce the risk of shingles (also called ]) and ] is caused by the same virus and is simply a larger-than-normal dose of Varivax, ] (VZV).
The ] (WHO) recommends ] only if a country can keep more than 80% of people vaccinated.<ref name=WHO2014/> If only 20% to 80% of people are vaccinated it is possible that more people will get the disease at an older age and outcomes overall may worsen.<ref name=WHO2014/> Either one or two doses of the vaccine are recommended.<ref name=WHO2014/> In the United States two doses are recommended starting at twelve to fifteen months of age.<ref name=CDC2015/> {{as of|2017|lc=n}}, twenty-three countries recommend all non-medically exempt children receive the vaccine, nine recommend it only for high-risk groups, three additional countries recommend use in only parts of the country, while other countries make no recommendation.<ref name="Wutzler_2017">{{cite journal | vauthors = Wutzler P, Bonanni P, Burgess M, Gershon A, Sáfadi MA, Casabona G | title = Varicella vaccination - the global experience | journal = Expert Review of Vaccines | volume = 16 | issue = 8 | pages = 833–843 | date = August 2017 | pmid = 28644696 | pmc = 5739310 | doi = 10.1080/14760584.2017.1343669 }}</ref> Not all countries provide the vaccine due to its cost.<ref name=Flatt2012>{{cite journal | vauthors = Flatt A, Breuer J | title = Varicella vaccines | journal = British Medical Bulletin | volume = 103 | issue = 1 | pages = 115–127 | date = September 2012 | pmid = 22859715 | doi = 10.1093/bmb/lds019 | doi-access = free }}</ref> In the ], Varilrix, a live viral vaccine<ref name="VarilixWeb">{{cite web | url=https://www.medicines.org.uk/emc/medicine/9787 | title=Varilrix | access-date=21 November 2021 | archive-date=28 July 2023 | archive-url=https://web.archive.org/web/20230728205740/https://www.medicines.org.uk/emc/medicine/9787 | url-status=live }}</ref> is approved from the age of 12 months, but only recommended for certain at risk groups.


<!-- Safety and formulations -->
==Dangers of chickenpox==
Minor side effects may include pain at the site of injection, fever, and rash.<ref name=CDC2015/> Severe side effects are rare and occur mostly in those with ].<ref name=WHO2014/> Its use in people with ] should be done with care.<ref name=WHO2014/> It is not recommended during ]; however, the few times it has been given during pregnancy no problems resulted.<ref name=CDC2015/><ref name=WHO2014/> The vaccine is available either by itself or along with the ], in a version known as the ].<ref name=WHO2014/> It is made from ].<ref name=CDC2015/>
Chickenpox is most often a mild disease, especially for children. Prior to the introduction of vaccine in 1995 in the US (released in 1988 in Japan & Korea), there were around 4,000,000 cases per year in the U.S., mostly children, with typically 100 or fewer deaths. Though mostly children caught it, the majority of deaths (by as much as 80%) were among adults. Additionally, chickenpox involved the hospitalization of about 10,000 people each year.<!--
--><ref name="WHO-Varicella vaccine">{{cite web | author=The Vaccines and other Biologicals department | publisher=WHO | title=Varicella vaccine | url=http://www.who.int/vaccines/en/varicella.shtml | date=May 2003 | accessdate=2006-08-18 |archiveurl = http://web.archive.org/web/20060813125255/http://www.who.int/vaccines/en/varicella.shtml <!-- Bot retrieved archive --> |archivedate = 2006-08-13}} - which includes:<br>{{cite journal | title=Varicella vaccines: WHO position paper | journal=Weekly Epidemiological Record | year=1998 | volume=73 | pages=241–248 | url=http://www.who.int/wer/pdf/1998/wer7332.pdf | format=PDF | pmid=9715106 | issue=32}}</ref>


<!-- Society and culture -->
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 hospitalizations have substantially declined in the U.S. due to vaccination,<!--
A live attenuated varicella vaccine, the Oka strain, was developed by ] and his colleagues in ] in the early 1970s.<ref name="Gershon_2007">{{cite book|vauthors=Gershon AA|chapter=Varicella-zoster vaccine|date=2007|chapter-url=http://www.ncbi.nlm.nih.gov/books/NBK47446/|title=Human Herpesviruses: Biology, Therapy, and Immunoprophylaxis|veditors=Arvin A, Campadelli-Fiume G, Mocarski E, Moore PS|place=Cambridge|publisher=Cambridge University Press|isbn=978-0521827140|pmid=21348127|access-date=6 February 2021|archive-date=23 November 2020|archive-url=https://web.archive.org/web/20201123205428/https://www.ncbi.nlm.nih.gov/books/NBK47446/|url-status=live}}</ref> American vaccinologist ]'s team developed a chickenpox vaccine in the United States in 1981, based on the "Oka strain" of the varicella virus.<ref name="Schillie_2018" /><ref name="www.historyofvaccines.org" /><ref name="embryo.asu.edu" /> The chickenpox vaccine first became commercially available in 1984.<ref name=WHO2014>{{cite journal | vauthors = | title = Varicella and herpes zoster vaccines: WHO position paper, June 2014 | journal = Relevé Épidémiologique Hebdomadaire | volume = 89 | issue = 25 | pages = 265–287 | date = June 2014 | pmid = 24983077 | hdl-access = free | hdl = 10665/242227 }}</ref> It is on the ].<ref name="WHO21st">{{cite book | vauthors = ((World Health Organization)) | title = World Health Organization model list of essential medicines: 21st list 2019 | year = 2019 | hdl = 10665/325771 | author-link = World Health Organization | publisher = World Health Organization | location = Geneva | id = WHO/MVP/EMP/IAU/2019.06. License: CC BY-NC-SA 3.0 IGO | hdl-access=free }}</ref><ref name="WHO22nd">{{cite book | vauthors = ((World Health Organization)) | title = World Health Organization model list of essential medicines: 22nd list (2021) | year = 2021 | hdl = 10665/345533 | author-link = World Health Organization | publisher = World Health Organization | location = Geneva | id = WHO/MHP/HPS/EML/2021.02 | hdl-access=free }}</ref>
--><ref name="Seward2002">{{cite journal | author=Seward JF, Watson BM, Peterson CL, ''et al.'' | title=Varicella disease after introduction of varicella vaccine in the United States, 1995&ndash;2000 | year=2002 | journal=JAMA | volume=287 | issue=5 | pages=606&ndash;11 | pmid=11829699 | url=http://jama.ama-assn.org/cgi/content/full/287/5/606 | accessdate=2006-05-01 | doi=10.1001/jama.287.5.606 }}</ref><!--
--><ref name="Nguyen2005">{{cite journal | author=Nguyen HQ, Jumaan AO, Seward JF | title=Decline in mortality due to varicella after implementation of varicella vaccination in the United States | journal=N Engl J Med | year=2005 | volume=352 | pages=450&ndash;8 | pmid=15689583 | url=http://content.nejm.org/cgi/content/abstract/352/5/450 | accessdate=2006-05-01 | doi=10.1056/NEJMoa042271 | issue=5 }}</ref><!--
--> though the rate of ] infection has increased for the same reason.<ref>{{cite journal |journal=Control Hosp. Epidemiol. |year=2008 |volume=29 |issue=12 |pages=1157–1163 |title=Herpes zoster-related hospitalizations and expenditures before and after introduction of the varicella vaccine in the United States |author= Patel MS, Gebremariam A, Davis MM |pmid=18999945 |doi=10.1086/591975}}</ref><ref>{{cite journal |journal=BMC Public Health |year=2005 |volume=5 |pages=68–68 |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 |author=Yih WK, Brooks DR, Lett SM, Jumaan AO, Zhang Z. Clements KM, Seward JF |pmid=15960856 |doi=10.1186/1471-2458-5-68 |pmc=1177968}}</ref><ref>{{cite journal |journal=Mayo Clin Proc.|year=2007 |volume=82 |issue=11 |pages=1341–1349 |title=A Population-Based Study of the Incidence and Complication Rates of Herpes Zoster Before Zoster Vaccine Introduction|author=Yawn BP, Saddier P, Wollan PC, St Sauver JL, Kurland MJ, Sy LS |pmid=17976353 |doi=10.4065/82.11.1341}}</ref> In 2006, the shingles vaccine was determined to be effective at preventing shingles (zoster) in persons 60 years of age and older, if administered regularly.<!--
--><ref name="Oxman2005">{{cite journal | author=Oxman MN, Levin MJ, Johnson GR, ''et al.'' | title=A vaccine to prevent herpes zoster and postherpetic neuralgia in older adults | journal=] | year=2005 | volume=352 |pages=2271&ndash;84 | pmid=15930418 | doi=10.1056/NEJMoa051016 | issue=22}}</ref> In 2011, the FDA approved Zostavax for those 50 to 59 years old.<ref>http://www.fda.gov/newsevents/newsroom/pressannouncements/ucm248390.htm</ref>


==Medical uses==
==Vaccination worldwide==
Varicella vaccine is 70% to 90% effective for preventing varicella and more than 95% effective for preventing severe varicella.<ref name="Pediatrics07">{{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 }}</ref> 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.<ref name="Pediatrics07" />


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.<ref name="cdc.gov">{{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 }}</ref> This has been the case of children who get the vaccine in their ] and later have contact with children with chickenpox. Some of these children may develop mild chickenpox also known as breakthrough disease.<ref>{{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}}</ref>
Japan was among the first countries to routinely vaccinate for chickenpox. Routine vaccination against varicella zoster virus is also performed in the ], 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 ] 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.


Another vaccine, known as ], 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 ] (also called herpes zoster) and ], which are caused by the same virus.<ref name="zostavax-cdc"/> The recombinant zoster (shingles) vaccine is recommended for adults aged 50 years and older.<ref>{{cite web | title=Recombinant Shingles VIS | website=U.S. ] (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}}</ref>
Vaccination is common in the United States, with 41 of the 50 states require immunization for children attending government-run schools. All 50 states offer a medical exemption, with 48 of those states also offering philosophical and/or religious exemptions. The vaccination is not routine in the United Kingdom. In the U.S. opinions that it should be dropped (individually or ]) are also sometimes voiced.


===Duration of immunity===
Other countries, such as ] and the ], 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 ] 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. It is feared that there would be a greater number of cases of shingles in adults, until the vaccination was given to the entire population—because adults who have had chickenpox as a child are less likely to have shingles in later life if they have been exposed occasionally to the chickenpox virus (for example by their children). This is because the exposure acts as a booster vaccine.<ref>{{dead link|date=February 2011}}</ref><ref>{{cite web|url=http://www.hpa.org.uk/infections/topics_az/chickenpox/gen_info.htm |title=UK Health Protection Agency ('&#39;Prevention'&#39; section) |publisher=Hpa.org.uk |date= |accessdate=2011-02-08}}</ref>
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.<ref name="Goldman2005">{{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 }}</ref>
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 6 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, and we are only now entering an era in the U.S. where the long-term efficacy of varicella vaccine can be accurately gauged.<!--
--><ref name="Goldman2005">{{cite journal | author=Goldman GS | title=Universal varicella vaccination: efficacy trends and effect on herpes zoster | journal=Int J Toxicol| volume=24| issue=4 | year=2005 | pages=205&ndash;213 | pmid=16126614 | doi=10.1080/10915810591000659}}</ref>


Some vaccinated children have been found to lose their protective antibodies in as little as five to eight years.<ref>{{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 }}</ref> However, according to the ] (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 (]) wanes – necessitating booster chickenpox vaccinations.<ref name="WHO-Varicella vaccine"/> 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.<ref name="CDCP-diseaseFAQs">{{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 }}</ref>
The vaccine is exceedingly safe: approximately 5% of children who receive the vaccine develop a fever or rash, but as of 1 May 2006, there have been no deaths yet attributable to the vaccine despite more than 40 million doses being administered.<!--
--><ref name="Wise2000">{{cite journal | author=Wise RP, Salive ME, Braun MM, ''et al.'' | title=Postlicensure safety surveillance for varicella vaccine | journal=JAMA | year=2000 | volume=284 | issue=10 | pages=1271&ndash;9 | pmid=10979114 | doi=10.1001/jama.284.10.1271 }}</ref>
Cases of vaccine-related chickenpox have been reported in patients with a weakened immune system,<!--
--><ref name="Wise2000"/><ref name="Quinlivan">{{cite journal | author=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 | year=2006 | journal=J Infect Dis | volume=193 | issue=7 | pages=927&ndash;30 | pmid=16518753 | doi=10.1086/500835 }}</ref><!--
--> but no deaths.


===Chickenpox===
The literature contains several reports of adverse reactions following varicella vaccination,<!--
]
--><ref name="Long list">For example:
Prior to the widespread introduction of the vaccine in the United States in 1995 (1986 in Japan and 1988 in Korea<ref name="Takahashi, 2001 Review">{{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 }}</ref>), 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.<ref name="Takahashi, 2001 Review" /><ref name="WHO-Varicella vaccine">{{cite web | author=The Vaccines and other Biologicals department | publisher=] (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 }}</ref><ref name=WHO2014 /><ref name="CDC">{{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=] (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 }}</ref> Most of the deaths were among young children.<ref name="Altman, NYT 1995.03.18 - Varicella vaccine licensure">{{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 }}</ref>
*{{cite journal | author=Ravkina LI, Matsevich GR | title=Morphological changes in the central nervous system in post-vaccinal encephalomyelitis developing after chickenpox vaccination in children | journal=Zh Nevropatol Psikhiatr Im S S Korsakova | year=1970 | volume=70 | issue=10 | pages=1465&ndash;71 | pmid=4395233 }}
*{{cite journal | author=Sunaga Y, Hikima A, Ostuka T, Morikawa A | title=Acute cerebellar ataxia with abnormal MRI lesions after varicella vaccination | journal=Pediatr Neurol | year=1995 | volume=13 | issue=4 | pages=340&ndash;2 | pmid=8771172 | doi=10.1016/0887-8994(95)00194-8 }}
*{{cite journal | author=Singer S, Johnson CE, Mohr R, Holowecky C | title=Urticaria following varicella vaccine associated with gelatin allergy | journal=Vaccine | year=1995 | volume=17 | issue=4 | pages=327&ndash;9 | pmid=9987170 | doi=10.1016/S0264-410X(98)00209-6}}
*{{cite journal | author=Gerecitano J, Friedman-Kien A, Chazen GD | title=Allergic reaction to varicella vaccine | journal=Ann Intern Med | year=1997 | volume=126 | issue=10 | pages=833&ndash;4 | pmid=9148672}}
*{{cite journal | author=Sakaguchi M, Yamanaka T, Ikeda K, Sano Y, Fujita H, Miura T, Inouye S | title=IgE-mediated systemic reactions to gelatin included in the varicella vaccine | journal=J Allergy Clin Immonol | year=1997 | volume=99 | issue=2 | pages=263&ndash;4 | pmid=9042057 | doi=10.1016/S0091-6749(97)70108-8 }}
*{{cite journal | author=Naruse H, Miwata H, Ozaki T, Asano Y, Namazue J, Yamanishi K | title=Varicella infection complicated with meningitis after immunization | journal=Acta Paediatr Jpn | year=1993 | volume=35 | issue=4 | pages=345&ndash;7 | pmid=8397466 }}
*{{cite journal | author=Lee SY, Komp DM, Andiman W | title=Thrombocytopenic Purpura following varicella-zoster vaccination | journal=Am J Pediatr Hematol Oncol | year=1986 | volume=8 | issue=1 | pages=78&ndash;80 | pmid=3013041 | doi=10.1097/00043426-198608010-00016 }}
*{{cite journal | author=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=Am J Epidem | year=2001 | volume=154 | issue=2 | pages=161&ndash;5 | pmid=11447050 | doi=10.1093/aje/154.2.161}}
*{{cite journal | author=Naseri A, Good WV, Cunningham ET Jr | title=Herpes zoster virus sclerokeratitis and anterior uveitis in a child following varicella vaccination | journal=Am J Ophthalmol | year=2003 | volume=135 | issue=3 | pages=415&ndash;7 | pmid=12614776 | doi=10.1016/S0002-9394(02)01957-8}}
*{{cite journal | author=Esmaeli-Gutstein B, Winkelman JZ | title=Uveitis associated with varicella virus vaccine | journal=Am J Ophthalmol | year=1999 | volume=127 | issue=6 | pages=733&ndash;4 | pmid=10372892 | doi=10.1016/S0002-9394(99)00059-8}}
*{{cite journal | author=Schwab J, Ryan M | title=Varicella zoster virus meningitis in a previously immunized child | journal=Pediatrics | year=2004 | volume=114 | issue=2 | pages=e273&ndash;4 | pmid=15286270 | doi=10.1542/peds.114.2.e273}}
*{{cite journal | author=Bronstein DE, Cotliar J, Votava-Smith JK, Powell MZ, Miller MJ, Cherry JD | title=Recurrent papular urticaria after varicella immunization in a 15-month-old girl | journal=Pediatr Infect Dis J | year=2005 | volume=24 | issue=3 | pages=269&ndash;70 | pmid=15750467 | doi=10.1097/01.inf.0000154330.47509.42}}
*{{cite journal | author=Binder NR, Holland GN, Hosea S, Silverberg ML | title=Herpes zoster ophthalmicus in an otherwise-healthy child | journal=J Aapos | year=2005 | volume=9 | issue=6 | pages=597&ndash;8 | pmid=16414532 |doi=10.1016/j.jaapos.2005.06.009}}</ref><!--
--> including vaccine-strain zoster in children and adults.<!--
--><ref name="Matsubara1995">{{cite journal | author=Matsubara K, Nigami H, Harigaya H, Baba K | title=Herpes zoster in a normal child after varicella vaccination | journal=Acta Paediatr Jpn | year=1995 | volume=37 | issue=5 | pages=648&ndash;50 | pmid=8533598}}</ref><!--
--><ref name="Hammerschlag1989">{{cite journal | author=Hammerschlag MR, Gershon AA, Steinberg SP, Clarke L, Gelb LD | title=Herpes zoster in an adult recipient of live attenuated varicella vaccine | journal=J Infect Dis | year=1989 | volume=160 | issue=3 | pages=535&ndash;7 | pmid=2547882 | doi=10.1093/infdis/160.3.535}}</ref>
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.


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,<ref name="Seward2002">{{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 }}</ref><ref name="Nguyen2005">{{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 }}</ref> though the rate of ] infection has increased as adults are less exposed to infected children (which would otherwise help protect against shingles).<ref>{{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 }}</ref><ref name="Yih2005">{{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 }}</ref><ref>{{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 }}</ref> 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%<ref name="CDC" /> and a 97% drop in chickenpox deaths among those under 20.<ref>{{cite news| vauthors =Szabo L |title=Vaccine has nearly eliminated chickenpox deaths in children|newspaper=]|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}}</ref>
==Administration==
This vaccine is a shot given in the ]. It is recommended for all children under 13 and for everyone 13 or older who has never had chickenpox.


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 ], 30% had lost the antibody after five years, and 8% had already caught wild chickenpox in those five years.<ref>{{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 }}</ref>
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.<ref>{{cite web|url=http://www.vaccineinformation.org/varicel/qandavax.asp|title=Who should get this vaccine?|date=|accessdate=May 5,2010}}</ref>


=== Herpes zoster ===
The varicella vaccine is not recommended for seriously ill people, ], people who have experienced a serious allergic reaction to the varicella vaccine in the past, people who are allergic to ], people allergic to ], people suffering from an immune system disease, such as ], people receiving high doses of ], people receiving treatment for ] with ], ] or ], as well as people who have received ] or ] during the past 5 months.<ref>{{cite web|url=http://familydoctor.org/online/famdocen/home/healthy/vaccines/193.html|title=Who should not receive the varicella vaccine?|date=|accessdate=May 5,2010}}</ref>
] (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.<ref name=Gershon2013 /><ref name=MMWR-Harpaz>{{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 }}</ref>

The risk of developing shingles is reduced for children who receive the varicella vaccine, but not eliminated.<ref name="cdc-hcps" /> 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."<ref>{{cite web|title=CDC – Varicella Vaccine – Vaccine Safety|website=] (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}}
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NB: THIS archived version of the article is similar to <ref name=CDC2015 /> except that that one does not include this quote, and this one does. (If you feel this ref is redundant, consider using this archive-url for <ref name=CDC2015 /> instead.)
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</ref>

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.<ref name="cdc-hcps">{{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 }}</ref><ref name="sa-shingles">{{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 }}</ref> A population with high varicella vaccination also has lower incidence of shingles in unvaccinated children, due to ].<ref name="sa-shingles" />

===Schedule===
The WHO recommends one or two doses with the initial dose given at 12 to 18 months of age.<ref name=WHO2014/> The second dose, if given, should occur at least one to three months later.<ref name=WHO2014/> The second dose, if given, provides the additional benefit of improved protection against all varicella.<ref>{{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 }}</ref> 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.<ref>{{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}}</ref>

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).<ref>{{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=] (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}}</ref> The varicella vaccine did not become widely available in the United States until 1995.<ref>{{cite web |url=https://www.cdc.gov/chickenpox/surveillance/monitoring-varicella.html |title=Monitoring the Impact of Varicella Vaccination |publisher=] (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 }}</ref>

In the UK, the vaccine is only available on the ] for those who are in close contact with someone who is particularly vulnerable to chickenpox.<ref name=NHS2>{{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 }}</ref> As there is an increased risk of ] 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.<ref name=NHS2/> 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.<ref name="VarilixWeb" />

==Contraindications==
The varicella vaccine is not recommended for seriously ill people, ] 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 ], people allergic to ], people receiving high doses of ], people receiving treatment for ] with ] or ], as well as people who have received ] or ] during the past five months.<ref>{{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}}</ref><ref name="Chickenpox VIS">{{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=] (CDC)}}</ref> Additionally, the varicella vaccine is not recommended for people who are taking ] (e.g. aspirin).<ref name="Chickenpox VIS" /> After receiving the varicella vaccine, the use of salicylates should be avoided for at least six weeks.<ref name="Chickenpox VIS" /> The varicella vaccine is also not recommended for individuals who have received a live vaccine in the last four weeks,<ref name="Chickenpox VIS" /> because live vaccines that are administered too soon within one another may not be as effective.<ref name="Chickenpox VIS" /> It may be usable in people with HIV infections who have a good blood count and are receiving appropriate treatment.<ref name=WHO2014/> Specific antiviral medication, such as acyclovir, famciclovir, or valacyclovir, are not recommended 24 hours before and 14 days after vaccination.<ref>{{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 }}</ref>


==Side effects== ==Side effects==
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 ] and ] have been reported (mainly in inadvertently vaccinated immunocompromised children) as well as ].<ref name=Gershon2013>{{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 }}</ref>
Serious side effects are very rare, however in rare occasions, some severe reactions have been reported such as ], ], and ].<ref>{{cite web|url=http://www.nlm.nih.gov/medlineplus/ency/article/007065.htm|title=Risks and Side Effects|date=|accessdate=May 5,2010}}</ref>


The possible mild side effects include redness, ], and ] at the injection site, as well as ]. A few people may develop a mild ] which usually appears around the shot's area.<ref>{{cite web|url=http://www.vaccineinformation.org/varicel/qandavax.asp|title=What side effects have been reported with this vaccine?|date=|accessdate=May 5,2010}}</ref> The possible mild side effects include redness, ], and ] at the injection site, as well as ]. A few people may develop a mild ], which usually appears around the injection site.<ref>{{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}}</ref>


There is a risk to develop ] (shingles) following vaccination. However, this risk is less than after infection with the varicella virus. Most of the cases reported have been mild and have not been associated with serious complications.<ref>{{cite web|url=http://www.vaccineinformation.org/varicel/qandavax.asp|title=Vaccine Information for the public and health professionals|date=|accessdate=May 5,2010}}</ref> There is a short-term risk of developing ] (shingles) following vaccination. However, this risk is less than the risk due to a natural infection resulting in chickenpox.<ref name="Andrews">{{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}}</ref>{{rp|378}} Most of the cases reported have been mild and have not been associated with serious complications.<ref>{{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 }}</ref>


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.<ref name="Galea2008">{{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 }}</ref> Cases of vaccine-related chickenpox have been reported in patients with a weakened immune system,<ref name="Wise2000">{{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 }}</ref><ref name="Quinlivan">{{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 }}</ref> but no deaths.
==Effectiveness==


The literature contains several reports of adverse reactions following varicella vaccination, including vaccine-strain zoster in children and adults.<ref name="Long list">For example:
According to the ], clinical trials have demonstrated that varicella vaccine is 70% to 90% effective for preventing varicella and more than 95% effective for preventing severe varicella.<ref>{{cite web|url=http://aappolicy.aappublications.org/cgi/content/full/pediatrics;105/1/136|title=Can the vaccine cause herpes zoster (shingles)?|date=|accessdate=May 5,2010}}</ref>
* {{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 }}</ref>
==History==
The varicella-zoster vaccine is made from the Oka/] 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 ] cell cultures, and finally propagated in a human ] cell line originally derived from ] tissues (]).<ref name="Varivax FDA label" /><ref name="FDA Varivax">{{cite web | title=Varivax | website=U.S. ] (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 }}</ref><ref name="FDA Varivax archive">{{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. ] (FDA)}}</ref> Takahashi and his colleagues used the Oka strain to develop a live attenuated varicella vaccine in Japan in the early 1970s.<ref name="Gershon_2007" /> This strain was further developed by pharmaceutical companies such as ] and ].<ref>{{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 }}</ref> American vaccinologist ]'s team at Merck then used the Oka strain to prepare a chickenpox vaccine in 1981.<ref name="Schillie_2018">{{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 }}</ref><ref name="www.historyofvaccines.org">{{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}}</ref><ref name="embryo.asu.edu">{{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}}</ref>


Japan was among the first countries to vaccinate for chickenpox. The vaccine developed by Hilleman was first licensed in the United States in 1995.<ref name="Schillie_2018" /><ref>{{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}}</ref> 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}}).<ref>{{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 }}</ref>
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 ] which indicated protection for at least 20 years.<ref>{{cite web|url=http://aappolicy.aappublications.org/cgi/content/full/pediatrics;105/1/136 |title=Duration of immunity|date=|accessdate=May 5,2010}}</ref>


{{as of|2019|lc=n}}, standalone varicella vaccines are available in all 27 ] member countries, and 16 countries also offer a combined ] (MMRV).<ref name="Spoulou2019">{{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 }}</ref> 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.<ref name="Spoulou2019"/> 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 ], the possible risk of ] when vaccinating older adults, and rare ] after the first dose of the MMRV vaccine.<ref name="Spoulou2019"/> "Countries that implemented UVV experienced decreases in varicella incidence, hospitalizations, and complications, showing overall beneficial impact."<ref name="Spoulou2019"/>
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 ] and later have contact with children with chickenpox. Some of these children may develop a mild chickenpox also known as breakthrough disease.<ref>{{cite web|url=http://www.hoptechno.com/chickenpox-vac.htm |title=Varicella Vaccine (Chickenpox)|date=|accessdate=May 5,2010}}</ref>


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 ] disorders;<ref name="cdc.gov"/> 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, ], adults who may be ] to varicella (for example, people who work with young children), immigrants and refugees from tropical regions, people receiving chronic ] therapy (for example, ] )," and others.<ref name="HealthCanadaHealthcareProGuide">{{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=] |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 }}</ref>
== Controversy ==
Mortality due to primary varicella has declined significantly in countries which make wide use of the varicella vaccine.<!--
--><ref name="Seward2002"/><!--
--><ref name="Wise2000"/>
Zoster (shingles) most often occurs in the elderly. Multiple studies have not observed any effect on zoster incidence. This may be because infants and children immunized in varicella vaccination programs have not yet reached the age where zoster typically occurs. It is likewise too early to observe the effect on ] (PHN).


Australia has adopted recommendations for routine immunization of children and susceptible adults against chickenpox.<ref>{{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 }}</ref>
It has been claimed that adult shingles may increase after introduction of varicella vaccine.<!--
--><ref name="Yih2005">{{cite journal | author=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 vaccination coverage, 1998-2003 | journal=BMC Public Health | volume=5| issue=1 | year=2005 | pages=68–68 | pmid=15960856 | doi=10.1186/1471-2458-5-68 | pmc=1177968}}</ref><!--
--><ref name="HerpesDoctor-506-Jack">{{cite web | author=Jack | title=Chickenpox Vaccine Linked with Shingles Epidemic | url=http://www.herpesdoctor.com/node/506 | publisher=HerpesDoctor | date=2005 | accessdate=2006-08-18}}</ref>
Preliminary evidence that this has occurred is available from data collected from the Antelope Valley Varicella Surveillance Project (VASP) which began surveillance of shingles in 2000. VASP case reports indicate there was a statistically significant increase in adult shingles cases reported to the Antelope Valley Varicella Active Surviellance Project (VASP) from 2000 to 2003. The 56.1% increase from 237 cases in 2000 to 370 cases in 2002 yields a rate ratio of 1.4 (95% C.I. 1.2-1.7). Increases in cases of shingles reported to VASP occurred in every age category (except 70+) from 2000 to 2001. VASP also reported that verified cases of shingles among adults aged 50 years and older increased 27.5% from 2006 to 2007. (Annual Summary, 2001, 2002, 2003, 2006, 2007 Antelope Valley Varicella Active Surveillance Project, Los Angeles County Department of Health Services; Centers for Disease Control and Prevention (CDC) Cooperative Agreement No. U66/CCU911165-10; Mascola L, et al.) <!--
--><ref name="Brisson2002">{{cite journal | author=Brisson M, Gay NJ, Edmunds WJ, Andrews NJ | title=Exposure to varicella boosts immunity to Herpes-zoster: implications for mass vaccination against varicella | journal=Vaccine | year=2002 | volume=20 | pages=2500&ndash;7 | pmid=12057605 | doi=10.1016/S0264-410X(02)00180-9 | issue=19-20}}</ref>


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 ], and by 2005 all ] 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.<ref>{{cite web |url=https://www.nhs.uk/conditions/vaccinations/chickenpox-vaccine-questions-answers/ |title=Chickenpox vaccine FAQs |website=].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 }}</ref>
Additional 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.<ref>{{cite web|url=http://www.cdc.gov/nip/vacsafe/concerns/gen/humancell.htm |title=NIP: Vacsafe/Concerns/Gen/Human Cell Cultures in Manufacturing Vaccines |publisher=Web.archive.org |date= |accessdate=2011-02-08 |archiveurl = http://web.archive.org/web/20070212172520/http://www.cdc.gov/nip/vacsafe/concerns/gen/humancell.htm |archivedate = 2007-02-12}}</ref>


Since 2013, the ] has been offered for free to all Brazilian citizens.<ref>{{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 }}</ref>
===Duration of immunity===
Some vaccinated children have been found to lose their protective antibody in as little as five to eight years.<ref>{{cite journal |author=Chaves SS, Gargiullo P, Zhang JX, ''et al.'' |title=Loss of vaccine-induced immunity to varicella over time |journal=N. Engl. J. Med. |volume=356 |issue=11 |pages=1121–9 |year=2007 |month=March |pmid=17360990 |doi=10.1056/NEJMoa064040 |url=}}</ref> However, according to the ]: "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.<!--
--><ref name="WHO-Varicella vaccine"/>
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).<!--
--><ref name="CDCP-diseaseFAQs">{{cite web | work=Varicella Disease (Chickenpox) | title=General questions about the disease | url=http://www.cdc.gov/nip/diseases/varicella/faqs-gen-disease.htm | date=December 20, 2001 | publisher=CDCP | accessdate=2006-08-18}}</ref>


==Society and culture==
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" (see below). Historically, exposure of adults to contagious children has boosted their immunity, reducing the risk of shingles.<ref name="HerpesDoctor-506-Jack"/>


===Catholic Church===
<!-- immunocompromise is a different topic really -->
{{Main|Use of fetal tissue in vaccine development#Position of the Catholic Church}}
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 use of fetal tissue in vaccine development is the practice of researching, developing, and producing ] through growing viruses in ] (laboratory-grown) ] that were originally derived from human ] 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.
--><ref>{{dead link|date=February 2011}}</ref><!--
--><ref>{{cite journal |author=Tugwell BD, Lee LE, Gillette H, Lorber EM, Hedberg K, Cieslak PR |title=Chickenpox outbreak in a highly vaccinated school population |journal=Pediatrics |volume=113 |issue=3 Pt 1 |pages=455–9 |year=2004 |month=March |pmid=14993534 |doi=10.1542/peds.113.3.455 |url=}}</ref><!--
--><ref>http://www.al.com/news/huntsvilletimes/index.ssf?/base/news/113464189674151.xml&coll=1</ref><!--
--><ref>{{dead link|date=February 2011}}</ref><!--
--><ref>{{cite web|author=By HealthiNation |url=http://health.yahoo.com/ency/healthwise/hw208205 |title=Yahoo! Health |publisher=Health.yahoo.com |date= |accessdate=2011-02-08}}</ref>


The ] is opposed to abortion. Nevertheless, the ] 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".<ref>{{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}}</ref> On 21 December 2020, the Vatican's doctrinal office, the ], 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".<ref name="CDPvaccines2020">{{cite journal |author1=] |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=] |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 }}</ref>
===Immunocompromise===
The mortality rate in immunocompromised patients with disseminated herpes zoster is 5-15%, with most deaths from ]. 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 ], 30% had lost the antibody after five years, and 8% had already caught wild chickenpox in that five year period.<!--
--><ref>{{cite journal | author = Pirofski L, Casadevall A | title = Use of licensed vaccines for active immunization of the immunocompromised host. | journal = Clin Microbiol Rev | volume = 11 | issue = 1 | pages = 1–26 | date=1 January 1998| pmid = 9457426 | url=http://cmr.asm.org/cgi/content/full/11/1/1?view=long&pmid=9457426 | pmc = 121373 }}</ref>


==Pox parties== == References ==
{{Main|Pox party}} {{Reflist}}
A "pox party" is a party held by parents for the purpose of infecting their children with childhood diseases. Similar ideas have applied to other diseases, e.g. ], but are now discouraged by doctors and health services due to the risk of serious injury or death (even in children, as described above) from acquiring the disease. The reasoning behind such parties is that guests exposed to the ] virus will contract the disease and develop strong and persistent ] at an age before disaster is likely, particularly from chickenpox or ]. The first reference to such a practice is the letter of ] to ] describing parties held in Istanbul for the purpose of ]&mdash;an effective technique for gaining immunity to ].<ref>{{dead link|date=February 2011}}</ref> Lady Montagu imported variolation to England.


==See also== == Further reading ==
* {{cite book | vauthors = ((World Health Organization)) | title = The immunological basis for immunization series : Module 10: Varicella-zoster virus | publisher = ] (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. ] (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 = ] (CDC) | location = Atlanta GA | url = https://www.cdc.gov/vaccines/pubs/surv-manual/ | date = 9 January 2020 }}


== External links ==
==References==
* {{cite web | title=Chickenpox Vaccine Information Statement | website=U.S. ] (CDC)| date=10 August 2021| url=https://www.cdc.gov/vaccines/hcp/vis/vis-statements/varicella.html }}
{{Reflist|2}}
* {{cite web | title=Chickenpox (Varicella) Vaccination | website=U.S. ] (CDC) | date=25 February 2021 | url=https://www.cdc.gov/vaccines/vpd/varicella/ }}
* {{MeshName|Chickenpox Vaccine}}


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