Editing Vaccine (section)

==Other contents==
{{Excerpt|Vaccine ingredients}}

===Adjuvants===
{{main|Immunologic adjuvant}}

Vaccines typically contain one or more [[adjuvant]]s, used to boost the immune response. Tetanus toxoid, for instance, is usually adsorbed onto [[alum]]. This presents the antigen in such a way as to produce a greater action than the simple aqueous tetanus toxoid. People who have an adverse reaction to adsorbed tetanus toxoid may be given the simple vaccine when the time comes for a booster.<ref>{{Cite journal|last1=Engler|first1=Renata J. M.|last2=Greenwood|first2=John T.|last3=Pittman|first3=Phillip R.|last4=Grabenstein|first4=John D.|date=1 August 2006|title=Immunization to Protect the US Armed Forces: Heritage, Current Practice, and Prospects|journal=Epidemiologic Reviews|volume=28|issue=1|pages=3–26|doi=10.1093/epirev/mxj003|issn=0193-936X|pmid=16763072|doi-access=free}}</ref>

In the preparation for the 1990 Persian Gulf campaign, the whole cell [[pertussis]] vaccine was used as an adjuvant for [[anthrax]] vaccine. This produces a more rapid immune response than giving only the anthrax vaccine, which is of some benefit if exposure might be imminent.<ref>{{Cite book|last1=Sox|first1=Harold C.|url=https://www.ncbi.nlm.nih.gov/books/NBK222854/|title=Vaccines|last2=Liverman|first2=Catharyn T.|last3=Fulco|first3=Carolyn E.|last4=War|first4=Institute of Medicine (US) Committee on Health Effects Associated with Exposures During the Gulf|date=2000|publisher=National Academies Press (US)|access-date=3 May 2019|archive-date=16 November 2021|archive-url=https://web.archive.org/web/20211116025125/https://www.ncbi.nlm.nih.gov/books/NBK222854/|url-status=live}}</ref>

===Preservatives===
Vaccines may also contain preservatives to prevent contamination with [[bacteria]] or [[fungi]]. Until recent years, the preservative [[thiomersal]] ({{a.k.a.}} ''Thimerosal'' in the US and Japan) was used in many vaccines that did not contain live viruses. As of 2005, the only childhood vaccine in the U.S. that contains thiomersal in greater than trace amounts is the influenza vaccine,<ref>{{cite web|title=Institute for Vaccine Safety – Thimerosal Table|url=http://www.vaccinesafety.edu/thi-table.htm|url-status=live|archive-url=https://web.archive.org/web/20051210210622/http://www.vaccinesafety.edu/thi-table.htm|archive-date=10 December 2005}}</ref> which is currently recommended only for children with certain risk factors.<ref>Wharton, Melinda E.; National Vaccine Advisory committee [https://www.hhs.gov/nvpo/vacc_plan/ "U.S.A. national vaccine plan"] {{webarchive|url=https://web.archive.org/web/20160504053302/http://www.hhs.gov/nvpo/vacc_plan|date=4 May 2016}}</ref> Single-dose influenza vaccines supplied in the UK do not list thiomersal in the ingredients. Preservatives may be used at various stages of the production of vaccines, and the most sophisticated methods of measurement might detect traces of them in the finished product, as they may in the environment and population as a whole.<ref>{{cite web|title=Measurements of Non-gaseous air pollutants > Metals|url=http://www.npl.co.uk/environment/vam/nongaseouspollutants/ngp_metals.html|archive-url=https://web.archive.org/web/20070929124159/http://www.npl.co.uk/environment/vam/nongaseouspollutants/ngp_metals.html|archive-date=29 September 2007|access-date=28 June 2020|website=npl.co.uk|publisher=National Physics Laboratory}}</ref>

Many vaccines need preservatives to prevent serious adverse effects such as ''[[Staphylococcus]]'' infection, which in one 1928 incident killed 12 of 21 children inoculated with a [[diphtheria]] vaccine that lacked a preservative.<ref>{{cite web|date=6 September 2007|title=Thimerosal in vaccines|url=https://www.fda.gov/BiologicsBloodVaccines/SafetyAvailability/VaccineSafety/UCM096228|url-status=live|archive-url=https://web.archive.org/web/20130106215029/https://www.fda.gov/BiologicsBloodVaccines/SafetyAvailability/VaccineSafety/UCM096228|archive-date=6 January 2013|access-date=1 October 2007|publisher=Center for Biologics Evaluation and Research, U.S. Food and Drug Administration}}</ref> Several preservatives are available, including thiomersal, [[phenoxyethanol]], and [[formaldehyde]]. Thiomersal is more effective against bacteria, has a better shelf-life, and improves vaccine stability, potency, and safety; however, in the U.S., the [[European Union]], and a few other affluent countries, it is no longer used as a preservative in childhood vaccines, as a precautionary measure due to its [[Mercury (element)|mercury]] content.<ref>{{cite journal|vauthors=Bigham M, Copes R|year=2005|title=Thiomersal in vaccines: balancing the risk of adverse effects with the risk of vaccine-preventable disease|journal=Drug Safety|volume=28|issue=2|pages=89–101|doi=10.2165/00002018-200528020-00001|pmid=15691220|s2cid=11570020}}</ref> Although [[Thiomersal controversy|controversial claims]] have been made that thiomersal contributes to [[autism spectrum disorder|autism]], no convincing scientific evidence supports these claims.<ref>{{cite journal|author-link=Paul Offit|vauthors=Offit PA|date=September 2007|title=Thimerosal and vaccines – a cautionary tale|journal=The New England Journal of Medicine|volume=357|issue=13|pages=1278–1279|doi=10.1056/NEJMp078187|pmid=17898096|s2cid=36318722|doi-access=free}}</ref> Furthermore, a 10–11-year study of 657,461 children found that the [[MMR vaccine and autism|MMR vaccine does not cause autism]] and actually reduced the risk of autism by seven percent.<ref>{{Cite news|date=5 March 2019|title=Another study, this one of 657k kids, finds MMR vaccine doesn't cause autism |newspaper=National Post|url=https://nationalpost.com/news/world/the-largest-ever-study-has-shown-the-measles-mumps-and-rubella-vaccine-is-linked-to-lower-rates-of-autism|access-date=13 March 2019}}</ref><ref>{{Cite news|last=Hoffman|first=Jan|date=5 March 2019|title=One More Time, With Big Data: Measles Vaccine Doesn't Cause Autism|work=The New York Times|url=https://www.nytimes.com/2019/03/05/health/measles-vaccine-autism.html|access-date=13 March 2019|issn=0362-4331|name-list-style=vanc|archive-date=12 March 2019|archive-url=https://web.archive.org/web/20190312175816/https://www.nytimes.com/2019/03/05/health/measles-vaccine-autism.html|url-status=live}}</ref>

===Excipients===
Beside the active vaccine itself, the following [[excipient]]s and residual manufacturing compounds are present or may be present in vaccine preparations:<ref name="cdc">{{cite web|author=CDC|date=12 July 2018|title=Ingredients of Vaccines – Fact Sheet|url=https://www.cdc.gov/vaccines/vac-gen/additives.htm|url-status=live|archive-url=https://web.archive.org/web/20091217193639/http://www.cdc.gov/vaccines/vac-gen/additives.htm|archive-date=17 December 2009|access-date=20 December 2009}}</ref>
* [[Aluminum]] salts or gels are added as [[adjuvant]]s. Adjuvants are added to promote an earlier, more potent response, and more persistent immune response to the vaccine; they allow for a lower vaccine dosage.
* [[Antibiotic]]s are added to some vaccines to prevent the growth of bacteria during production and storage of the vaccine.
* Egg [[protein]] is present in the [[influenza vaccine]] and [[yellow fever vaccine]] as they are prepared using chicken eggs. Other proteins may be present.
* [[Formaldehyde]] is used to inactivate bacterial products for toxoid vaccines. Formaldehyde is also used to inactivate unwanted viruses and kill bacteria that might contaminate the vaccine during production.
* [[Monosodium glutamate]] (MSG) and 2-[[phenoxyethanol]] are used as stabilizers in a few vaccines to help the vaccine remain unchanged when the vaccine is exposed to heat, light, acidity, or humidity.
* [[Thiomersal]] is a mercury-containing antimicrobial that is added to vials of vaccines that contain more than one dose to prevent contamination and growth of potentially harmful bacteria. Due to the controversy surrounding thiomersal, it has been removed from most vaccines except multi-use influenza, where it was reduced to levels so that a single dose contained less than a microgram of mercury, a level similar to eating ten grams of canned tuna.<ref name="FDA">The mercury levels in the table, unless otherwise indicated, are taken from [https://www.fda.gov/Food/FoodborneIllnessContaminants/Metals/ucm115644.htm Mercury Levels in Commercial Fish and Shellfish (1990–2010)] {{webarchive|url=https://web.archive.org/web/20150503155319/https://www.fda.gov/Food/FoodborneIllnessContaminants/metals/ucm115644.htm|date=3 May 2015}} U.S. Food and Drug Administration. Accessed 8{{spaces}}January 2012.</ref>