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Herd Immunity and Implications for SARS-CoV-2 Control

Educational Objective
To identify the key insights or developments described in this article
1 Credit CME

Herd immunity, also known as indirect protection, community immunity, or community protection, refers to the protection of susceptible individuals against an infection when a sufficiently large proportion of immune individuals exist in a population. In other words, herd immunity is the inability of infected individuals to propagate an epidemic outbreak due to lack of contact with sufficient numbers of susceptible individuals. It stems from the individual immunity that may be gained through natural infection or through vaccination. The term herd immunity was initially introduced more than a century ago. In the latter half of the 20th century, the use of the term became more prevalent with the expansion of immunization programs and the need for describing targets for immunization coverage, discussions on disease eradication, and cost-effectiveness analyses of vaccination programs.1

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Article Information

Corresponding Author: Saad B. Omer, MBBS, MPH, PhD, Yale University, 1 Church St, New Haven, CT 06510 (saad.omer@yale.edu).

Published Online: October 19, 2020. doi:10.1001/jama.2020.20892

Conflict of Interest Disclosures: Dr Yildirim reported being a member of the mRNA-1273 Study Group. No other disclosures were reported.

References
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Fine  P , Eames  K , Heymann  DL .  “Herd immunity”: a rough guide.   Clin Infect Dis. 2011;52(7):911-916. doi:10.1093/cid/cir007PubMedGoogle ScholarCrossref
2.
Reproduction number (R) and growth rate (r) of the COVID-19 epidemic in the UK: methods of estimation, data sources, causes of heterogeneity, and use as a guide in policy formulation. The Royal Society. Preprint posted August 24, 2020. Accessed October 16, 2020. https://royalsociety.org/-/media/policy/projects/set-c/set-covid-19-R-estimates.pdf
3.
van den Driessche  P .  Reproduction numbers of infectious disease models.   Infect Dis Model. 2017;2(3):288-303.PubMedGoogle Scholar
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Edridge  AWD , Kaczorowska  J , Hoste  ACR ,  et al.  Seasonal coronavirus protective immunity is short-lasting.   Nat Med. Published online September 14, 2020. doi:10.1038/s41591-020-1083-1PubMedGoogle Scholar
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Christakis  NA , Fowler  JH .  Social network sensors for early detection of contagious outbreaks.   PLoS One. 2010;5(9):e12948. doi:10.1371/journal.pone.0012948PubMedGoogle Scholar
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Mateus  J , Grifoni  A , Tarke  A ,  et al.  Selective and cross-reactive SARS-CoV-2 T cell epitopes in unexposed humans.   Science. 2020;370(6512):89-94. doi:10.1126/science.abd3871PubMedGoogle ScholarCrossref
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Initial results from ongoing investigation of antibodies to COVID-19 virus. Public Health Agency of Sweden. Published May 20, 2020. Accessed September 30, 2020. https://www.folkhalsomyndigheten.se/nyheter-och-press/nyhetsarkiv/2020/maj/forsta-resultaten-fran-pagaende-undersokning-av-antikroppar-for-covid-19-virus/
8.
Stringhini  S , Wisniak  A , Piumatti  G ,  et al.  Seroprevalence of anti-SARS-CoV-2 IgG antibodies in Geneva, Switzerland (SEROCoV-POP): a population-based study.   Lancet. 2020;396(10247):313-319. doi:10.1016/S0140-6736(20)31304-0PubMedGoogle ScholarCrossref
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Pollán  M , Pérez-Gómez  B , Pastor-Barriuso  R ,  et al; ENE-COVID Study Group.  Prevalence of SARS-CoV-2 in Spain (ENE-COVID): a nationwide, population-based seroepidemiological study.   Lancet. 2020;396(10250):535-544. doi:10.1016/S0140-6736(20)31483-5 PubMedGoogle ScholarCrossref
10.
Anand  S , Montez-Rath  M , Han  J ,  et al.  Prevalence of SARS-CoV-2 antibodies in a large nationwide sample of patients on dialysis in the USA: a cross-sectional study.   Lancet. Published online September 25, 2020. doi:10.1016/S0140-6736(20)32009-2 PubMedGoogle Scholar
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Credit Designation Statement: The American Medical Association designates this Journal-based CME activity activity for a maximum of 1.00  AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Successful completion of this CME activity, which includes participation in the evaluation component, enables the participant to earn up to:

  • 1.00 Medical Knowledge MOC points in the American Board of Internal Medicine's (ABIM) Maintenance of Certification (MOC) program;;
  • 1.00 Self-Assessment points in the American Board of Otolaryngology – Head and Neck Surgery’s (ABOHNS) Continuing Certification program;
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  • 1.00 Lifelong Learning points in the American Board of Pathology’s (ABPath) Continuing Certification program; and
  • 1.00 credit toward the CME [and Self-Assessment requirements] of the American Board of Surgery’s Continuous Certification program

It is the CME activity provider's responsibility to submit participant completion information to ACCME for the purpose of granting MOC credit.

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