Editing Herd immunity (section)

==Free riding==
Herd immunity is vulnerable to the [[free rider problem]].<ref name=Barrett2014>{{cite book|vauthors=Barrett S|year=2014|title=Too Global To Fail: The World Bank at the Intersection of National and Global Public Policy in 2025|editor1=J. Warren Evans|editor2=Robin Davies|chapter=Global Public Goods and International Development|publisher=World Bank Publications|pages=13–18|isbn=978-1464803109}}</ref> Individuals who lack immunity, including those who choose not to vaccinate, free ride off the herd immunity created by those who are immune.<ref name=Barrett2014/> As the number of free riders in a population increases, outbreaks of preventable diseases become more common and more severe due to loss of herd immunity.<ref name="pmid22926181">{{cite journal |vauthors=Quadri-Sheriff M, Hendrix KS, Downs SM, Sturm LA, Zimet GD, Finnell SM |date=September 2012 |title=The role of herd immunity in parents' decision to vaccinate children: a systematic review |journal=Pediatrics |volume=130 |issue=3 |pages=522–30 |doi=10.1542/peds.2012-0140 |pmid=22926181 |doi-access=free}}</ref><ref name="pmid23584253">{{cite journal |vauthors=Dubé E, Laberge C, Guay M, Bramadat P, Roy R, Bettinger J |date=August 2013 |title=Vaccine hesitancy: an overview |journal=Human Vaccines & Immunotherapeutics |volume=9 |issue=8 |pages=1763–73 |doi=10.4161/hv.24657 |pmc=3906279 |pmid=23584253}}</ref><ref name="pmid23807359">{{cite journal |vauthors=Ropeik D |date=August 2013 |title=How society should respond to the risk of vaccine rejection |journal=Human Vaccines & Immunotherapeutics |volume=9 |issue=8 |pages=1815–8 |doi=10.4161/hv.25250 |pmc=3906287 |pmid=23807359}}</ref><ref name=pmid20667876/><ref name=stubborn/> Individuals may choose to free ride or be [[Vaccine hesitancy|hesitant to vaccinate]] for a variety of reasons, including the belief that vaccines are ineffective,<ref name=pmid23744504/> or that the risks associated with vaccines are greater than those associated with infection,<ref name=pmid21427399/><ref name=pmid23584253/><ref name=pmid23807359/><ref name=pmid23744504/> mistrust of vaccines or public health officials,<ref name=pmid23733039>{{cite journal|vauthors=Ozawa S, Stack ML|title=Public trust and vaccine acceptance--international perspectives|journal=Human Vaccines & Immunotherapeutics|volume=9|issue=8|pages=1774–8|date=August 2013|pmid=23733039|pmc=3906280|doi=10.4161/hv.24961 }}</ref> [[Bandwagon effect|bandwagoning]] or [[groupthink]]ing,<ref name=pmid20667876/><ref>{{cite journal|vauthors=Parker AM, Vardavas R, Marcum CS, Gidengil CA|title=Conscious consideration of herd immunity in influenza vaccination decisions|journal=American Journal of Preventive Medicine|volume=45|issue=1|pages=118–121|date=July 2013|pmid=23790997|pmc=3694502|doi=10.1016/j.amepre.2013.02.016}}</ref> social norms or [[peer pressure]],<ref name=pmid23744504>{{cite journal|vauthors=Gowda C, Dempsey AF|title=The rise (and fall?) of parental vaccine hesitancy|journal=Human Vaccines & Immunotherapeutics|volume=9|issue=8|pages=1755–62|date=August 2013|pmid=23744504|pmc=3906278|doi=10.4161/hv.25085}}</ref> and religious beliefs.<ref name=pmid23584253/> Certain individuals are more likely to choose not to receive vaccines if vaccination rates are high enough to convince a person that he or she may not need to be vaccinated, since a sufficient percentage of others are already immune.<ref name=pmid21427399/><ref name=stubborn/>