Editing Immune system (section)

===Vaccination===
{{Further|Vaccination}}
[[File:Polio Vaccination - Egypt (16868521330).jpg|right|thumb|Polio vaccination in Egypt|alt= A child receiving drops of polio vaccine in her mouth]]
Long-term ''active'' memory is acquired following infection by activation of B and T cells. Active immunity can also be generated artificially, through [[vaccination]]. The principle behind vaccination (also called [[immunization]]) is to introduce an [[antigen]] from a pathogen to stimulate the immune system and develop [[specific immunity]] against that particular pathogen without causing disease associated with that organism.{{sfn | Reece | 2011 | p=965}} This deliberate induction of an immune response is successful because it exploits the natural specificity of the immune system, as well as its inducibility. With infectious disease remaining one of the leading causes of death in the human population, vaccination represents the most effective manipulation of the immune system mankind has developed.{{sfn| Janeway |2005 |p=}}<ref>[https://www.who.int/healthinfo/bod/en/index.html Death and DALY estimates for 2002 by cause for WHO Member States.] {{Webarchive|url=https://web.archive.org/web/20081021133659/http://www.who.int/healthinfo/bod/en/index.html |date=21 October 2008 }} [[World Health Organization]]. Retrieved on 1 January 2007.</ref>

Many vaccines are based on [[non-cellular life|acellular]] components of micro-organisms, including harmless [[toxin]] components.{{sfn | Reece | 2011 | p=965}} Since many antigens derived from acellular vaccines do not strongly induce the adaptive response, most bacterial vaccines are provided with additional [[Immunologic adjuvant|adjuvants]] that activate the [[antigen-presenting cell]]s of the innate immune system and maximize [[immunogenicity]].<ref>{{cite journal | vauthors = Singh M, O'Hagan D | title = Advances in vaccine adjuvants | journal = Nature Biotechnology | volume = 17 | issue = 11 | pages = 1075–81 | date = Nov 1999 | pmid = 10545912 | doi = 10.1038/15058 | s2cid = 21346647 | doi-access = free }}</ref>