Editing Herd immunity (section)

===Passive immunity===
{{Main|Passive immunity}}

Individual immunity can also be gained passively, when [[Antibody|antibodies]] to a pathogen are transferred from one individual to another. This can occur naturally, whereby [[Mother#Biological mother|maternal]] antibodies, primarily [[immunoglobulin G]] antibodies, are transferred across the [[Placenta#Immunity|placenta]] and in [[colostrum]] to fetuses and newborns.<ref name=pmid20956021>{{cite journal|vauthors=Chucri TM, Monteiro JM, Lima AR, Salvadori ML, Kfoury JR, Miglino MA|title=A review of immune transfer by the placenta|journal=Journal of Reproductive Immunology|volume=87|issue=1–2|pages=14–20|date=December 2010|pmid=20956021|doi=10.1016/j.jri.2010.08.062}}</ref><ref>{{cite journal|vauthors=Palmeira P, Quinello C, Silveira-Lessa AL, Zago CA, Carneiro-Sampaio M|title=IgG placental transfer in healthy and pathological pregnancies|journal=Clinical & Developmental Immunology|volume=2012|pages=985646|year=2012|pmid=22235228|pmc=3251916|doi=10.1155/2012/985646|doi-access=free}}</ref> Passive immunity can also be gained artificially, when a susceptible person is injected with antibodies from the [[Serum (blood)|serum]] or [[Blood plasma|plasma]] of an immune person.<ref name=pville/><ref name=parija>{{cite book|vauthors=Parija SC|year=2014|title=Textbook of Microbiology & Immunology|url=https://books.google.com/books?id=bA9tAwAAQBAJ&pg=PA88|publisher=Elsevier Health Sciences|pages=88–89|isbn=978-8131236246|access-date=30 March 2015|archive-date=1 May 2021|archive-url=https://web.archive.org/web/20210501053035/https://books.google.com/books?id=bA9tAwAAQBAJ&pg=PA88|url-status=live}}</ref>

Protection generated from passive immunity is immediate, but wanes over the course of weeks to months, so any contribution to herd immunity is temporary.<ref name=ska/><ref name=pville/><ref name=gph>{{cite book|vauthors=Detels R, Gulliford M, Karim QA, Tan CC|year=2015|title=Oxford Textbook of Global Public Health|url=https://books.google.com/books?id=_ehcBgAAQBAJ&pg=PA1490|publisher=Oxford University Press|page=1490|isbn=978-0199661756|access-date=30 March 2015|archive-date=1 May 2021|archive-url=https://web.archive.org/web/20210501052956/https://books.google.com/books?id=_ehcBgAAQBAJ&pg=PA1490|url-status=live}}</ref> For diseases that are especially severe among fetuses and newborns, such as influenza and tetanus, pregnant women may be immunized in order to transfer antibodies to the child.<ref name=pmid23910028/><ref>{{cite journal|vauthors=Demicheli V, Barale A, Rivetti A|title=Vaccines for women for preventing neonatal tetanus|journal=The Cochrane Database of Systematic Reviews|issue=7|pages=CD002959|date=July 2015|volume=2015 |pmid=26144877|pmc=7138051|doi=10.1002/14651858.CD002959.pub4}}</ref><ref>{{cite journal|vauthors=Swamy GK, Garcia-Putnam R|title=Vaccine-preventable diseases in pregnancy|journal=American Journal of Perinatology|volume=30|issue=2|pages=89–97|date=February 2013|pmid=23271378|doi=10.1055/s-0032-1331032|s2cid=206342684 }}</ref> In the same way, high-risk groups that are either more likely to experience infection, or are more likely to develop complications from infection, may receive antibody preparations to prevent these infections or to reduce the severity of symptoms.<ref name=parija/>