'''Vaksin''' nyaéta préparasi nu dipaké pikeun ngaronjatkeun imunitas kana hiji inféksi panyakit. Ieu istilah diturunkeun tina istilah [[cacar sapi]]na [[Edward Jenner]] ("vacca" téh [[basa Latin]] nu hartina [[sapi]]), nu mun disuntikkeun ka [[manusa]] bakal ngajaga manusa tina panyakit [[cacar]]. Vaksin téh dumasar kana konsép [[variolasi]] nu asalna ti nagara [[Tiongkok]], nyaéta prakprakan népakeun cacar anu watekna lemah. Jenner sadar yén para wanoja anu ngolah susu [[sapi]] (jaman baheula di kulon biasana wanoja anu disebut ''milkmaid'') anu katépaan cacar sapi, henteu kabancén ku cacar. Dipakéna vaksin téh disebutna vaksinasi. Vaksinasi mangrupakeunmangrupa métode nu paling éféktif jang nyegah tina kasakitpanyakit nu nular. Vaksinasi efektif jangkeur ngaronjatkeun ningkatkeunkawedelan kekebalanawak, contohna baéwaé tina panyakit cacar, polio, campak jeung tetanus. Dumasar kana éféktivitasna nu geus diajaran jeung divérifikasi sacara luas, vaksin nu kaasup geus terbukti éféktif nyaéta saperti vaksin [[influénza]]<ref>{{Cite book|title=Vaccines for Pandemic Influenza|last=Fiore|editor-first2=Walter A.|editor-last=Compans|editor-first=Richard W.|last3=Cox|first3=Nancy J.|last2=Bridges|first2=Carolyn B.|first=Anthony E.|url=https://doi.org/10.1007/978-3-540-92165-3_3|language=en|doi=10.1007/978-3-540-92165-3_3|series=Current Topics in Microbiology and Immunology|pages=43–82|isbn=978-3-540-92165-3|location=Berlin, Heidelberg|date=2009|publisher=Springer|editor-last2=Orenstein}}</ref>, vaksin HPV<ref>{{Cite journal|last=Chang|first=Yuli|last2=Brewer|first2=Noel T.|last3=Rinas|first3=Allen C.|last4=Schmitt|first4=Karla|last5=Smith|first5=Jennifer S.|date=2009-07-09|title=Evaluating the impact of human papillomavirus vaccines|url=http://www.sciencedirect.com/science/article/pii/S0264410X09003831|journal=Vaccine|language=en|volume=27|issue=32|pages=4355–4362|doi=10.1016/j.vaccine.2009.03.008|issn=0264-410X}}</ref> jeung vaksin cacar air.<ref>{{Cite journal|last=Liesegang|first=Thomas J.|date=2009-08-01|title=Varicella zoster virus vaccines: effective, but concerns linger|url=https://www.canadianjournalofophthalmology.ca/article/S0008-4182(09)80185-3/abstract|journal=Canadian Journal of Ophthalmology|language=English|volume=44|issue=4|pages=379–384|doi=10.3129/i09-126|issn=0008-4182|pmid=19606157}}</ref> Organisasi Kaséhatan Dunia (WHO) ngalaporkeun sangkan vaksin nu geus miboga izin ayeuna aya jang dua puluh lima inféksi nu bisa dicegah.<ref>{{Cite web|url=https://www.who.int/teams/immunization-vaccines-and-biologicals/strategies/global-vaccine-action-plan|title=Global Vaccine Action Plan|website=www.who.int|language=en|accessdate=2020-12-07}}</ref>
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Vaccines can be [[prophylaxis|prophylactic]] (e.g. to prevent or ameliorate the effects of a future [[infection]] by any natural or "wild" [[pathogen]]), or [[Drug therapy|therapeutic]] (e.g. vaccines against cancer are also being investigated; see [[cancer vaccine]]).
