Immunisation for the Sake of the ‘Herd’


Individuals who vaccinate directly benefit from the protection it affords them against contracting a specific disease. However, others will often also benefit, as vaccinated individuals cannot transmit the disease. Herd immunity refers to the indirect protection against infectious disease that unvaccinated, or nonimmune, individuals receive as a result of reduced disease transmission due to the presence of vaccinated, or immune, individuals. Herd immunity is important, particularly for individuals who cannot be vaccinated because of age or contraindications, who do not get vaccinated because of refusal, those for whom immunisation is ineffective or for whom immunity has waned due to age. Even when vaccination coverage in a given population is high, certain communities may be at risk of outbreaks if significant numbers of people choose not to vaccinate. Therefore, vaccine hesitancy and vaccine refusal threaten herd immunity. Policymakers can use vaccine mandates to increase vaccination coverage to promote herd immunity.

Key Concepts

  • Herd immunity refers to the indirect protection against infectious disease that unvaccinated, or nonimmune, individuals receive as a result of reduced disease transmission due to the presence of vaccinated, or immune, individuals.
  • Herd immunity can provide protection for individuals who cannot be vaccinated because of age or contraindications, who do not get vaccinated because of refusal or other reasons and for those whom vaccination is ineffective.
  • Even if vaccination coverage in a population is high, vaccines are not perfect, so certain communities may be at risk for outbreaks of infectious disease if the vaccination coverage dips below the herd immunity threshold, such that disease transmission can take place.
  • Although some individuals may be tempted to forego immunisation, believing they are protected by the vaccination of others around them (herd immunity), nonvaccinated individuals are at higher risk for contracting infectious diseases. For certain diseases, the severity of illness may be increased if contracted at an older age due to delayed exposure (herd severity effect).
  • Public support of vaccination programmes, such as the National Vaccine Injury Compensation Program in the United States, is justified at least partially because vaccination at the individual level indirectly benefits the health of the population at large.

Keywords: herd immunity; immunisation; herd immunity threshold; reproduction number; vaccine hesitancy; vaccine refusal; vaccine mandates; vaccination coverage; herd severity effect

Figure 1. Educational graphic demonstrating benefits of herd immunity. Courtesy of the United States Centers for Disease Control and Prevention (CDC) 2017.


AdegbolaRA, SeckaO, LahaiG, et al. (2005) Elimination of Haemophilus influenzae type b (Hib) disease from The Gambia after the introduction of routine immunisation with a Hib conjugate vaccine: a prospective study. Lancet366: 144–150.

AlexanderE (1961) The extent of the poliomyelitis problem. JAMA175: 837–840.

AliM, EmchM, vonSeidleinL, et al. (2005) Herd immunity conferred by killed oral cholera vaccines in Bangladesh: a reanalysis. Lancet366: 44–49.

AndreFE, BooyR, BockHL, et al. (2008) Vaccination greatly reduces disease, disability, death and inequity worldwide. Bulletin of the World Health Organization86: 140–146.

BlankNR, CaplanAL and ConstableC (2013) Exempting schoolchildren from immunizations: states with few barriers had highest rates of nonmedical exemptions. Health Affairs32: 1282–1290.

BrewerNT and MossJL (2015) Herd immunity and the herd severity effect. Lancet Infectious Diseases15: 868–869.

BrissonM and EdmundsWJ (2003) Economic evaluation of vaccination programs: the impact of herd‐immunity. Medical Decision Making23: 76–82.

CaplanA (2013) Liberty has its responsibilities. Human Vaccines & Immunotherapeutics9: 2666–2667.

Centers for Disease Control and Prevention (CDC) (1994) Outbreak of measles among Christian Science Students – Missouri and Illinois. Morbidity and Mortality Weekly Report43: 463–465.

Centers for Disease Control and Prevention (CDC) (2017) What Would Happen if We Stopped Vaccinations?‐gen/whatifstop.htm (accessed 18 Dec 2017).

ChenRT, RastogiSC, MullenJR, et al. (1994) The vaccine adverse event reporting system (VAERS). Vaccine12: 542–550.

ColgroveJ (2006) State of Immunity: The Politics of Vaccination in Twentieth‐Century America. Berkeley, CA: University of California Press.

EamesKT (2009) Networks of influence and infection: parental choices and childhood disease. Journal of the Royal Society Interface6: 811–814.

FeffermanNH and NaumovaEN (2015) Dangers of vaccine refusal near the herd immunity threshold: a modelling study. Lancet Infectious Diseases15: 922–926.

FeikinDR, LezotteDC, HammanRF, et al. (2000) Individual and community risks of measles and pertussis associated with personal exemptions to immunization. JAMA284: 3145–3150.

FieldRI and CaplanAL (2008) A proposed ethical framework for vaccine mandates: competing values and the case of HPV. Kennedy Institute of Ethics Journal18: 111–124.

FinePE (1993) Herd immunity: history, theory, practice. Epidemiologic Reviews15: 265–302.

FineP, EamesK and HeymannDL (2011) “Herd immunity”: a rough guide. Clinical Infectious Diseases52: 911–916.

FinePEM, MulhollandK, ScottJA and EdmundsWJ (2017) Community protection. In: PlotkinS, OrensteinW, Offit and EdwardsKM (eds) Plotkin's Vaccines, pp. 1512–1531.e1515. Elsevier.

FoxJP, ElvebackL, ScottW, et al. (1971) Herd immunity: basic concept and relevance to public health immunization practices. American Journal of Epidemiology94: 179–189.

HendersonDA, DunstonFJ, FedsonDS, et al. (1991) The measles epidemic: the problems, barriers, and recommendations. JAMA266: 1547–1552.

HendrixKS, FinnellSME, ZimetGD, et al. (2014) Vaccine message framing and parents' intent to immunize their infants for MMR. Pediatrics134: e675–e683.

Immunization Action Coalition (IAC) (2017) State Information: Exemptions Permitted for State Immunization Requirements. (accessed 23 Apr 2018).

JansenVA, StollenwerkN, JensenHJ, et al. (2003) Measles outbreaks in a population with declining vaccine uptake. Science301: 804.

JohnTJ and SamuelR (2000) Herd immunity and herd effect: new insights and definitions. European Journal of Epidemiology16: 601–606.

LookerC and KellyH (2011) No‐fault compensation following adverse events attributed to vaccination: a review of international programmes. Bulletin of the World Health Organization89: 371–378.

MelloMM (2008) Rationalizing vaccine injury compensation. Bioethics22: 32–42.

MoultonLH, ChungS‐e, CrollJ, et al. (2000) Estimation of the indirect effect of Haemophilus influenzae type b conjugate vaccine in an American Indian population. International Journal of Epidemiology29: 753–756.

Quadri‐SheriffM, HendrixKS, DownsSM, et al. (2012) The role of herd immunity in parents' decision to vaccinate children: a systematic review. Pediatrics130: 522–530.

SchlenkerTL, BainC, BaughmanAL and HadlerSC (1992) Measles herd immunity: the association of attack rates with immunization rates in preschool children. JAMA267: 823–826.

SchwartzJL and CaplanAL (2011) Vaccination refusal: ethics, individual rights, and the common good. Primary Care; Clinics in Office Practice38: 717–728.

SoboEJ (2016) What is herd immunity, and how does it relate to pediatric vaccination uptake? US parent perspectives. Social Science and Medicine165: 187–195.

StephensDS (2008) Vaccines for the unvaccinated: protecting the herd. Journal of Infectious Diseases197: 643–645.

TopleyWWC and WilsonGS (1923) The spread of bacterial infection. The problem of herd‐immunity. Journal of Hygiene21: 243–249.

U.S. Health Resources & Services Administration (2017) National Vaccine Injury Compensation Program.‐compensation/index.html (accessed 18 Dec 2017).

Further Reading

PlotkinSA, OrensteinW and OffitPA (eds) (2017) Plotkin's Vaccines, 7th, 1720 pp edn. Philadelphia, PA: W.B. Saunders Co. (Elsevier).

SchwartzJL and CaplanAL (eds) (2017) Vaccination Ethics and Policy: An Introduction with Readings, 432 pp. Cambridge, MA: MIT Press.

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How to Cite close
Chapman, Carolyn R, and Caplan, Arthur L(Mar 2018) Immunisation for the Sake of the ‘Herd’. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0027995]