Thursday, March 31, 2022
Achieving classical flock immunity to SARS-CoV-2, the virus that causes COVID-19, may not be achievable, according to a new perspective published in Journal of Infectious Diseases. However, widespread use of currently available public health interventions to prevent and control COVID-19 will allow resumption of most activities of daily living with minimal disruption, the authors note. Anthony S. Fauci, MD, Director of the National Institute of Allergy and Infectious Diseases (NIAID), Part of the NIH, David M. Morens, MD, Senior Scientific Advisor to the NIAID Director, and Gregory K. Folkers, Chief of Staff to the NIAID the director authored the perspective.
The general concept of herd immunity implies that transmission of an infectious agent can be detected, except for sporadic outbreaks, because a certain part of the population is already protected through vaccination or prior infection. The authors explain how the scientific understanding of herd immunity and its application to various diseases has evolved over time. High levels of herd immunity have enabled the United States to control polio and measles to a large extent – two diseases caused by viruses that have not undergone significant development. The authors note, however, that the benefits of achieving flock immunity thresholds have been less successful with respiratory viruses such as influenza, which are constantly mutating.
Dr. Fauci and his colleagues write that it is unlikely to achieve classical herd immunity to SARS-CoV-2, due to a combination of factors that include features of the virus as well as current societal dynamics. These include the virus’ ability to continuously mutate into new variants; asymptomatic virus transmission, which complicates public health control strategies; inability of prior infection or vaccination to provide lasting protection against re-infection; suboptimal vaccination coverage; and compliance with non-pharmacological interventions.
However, the authors note that it is now possible to control COVID-19 without major disruption in society due to widespread background immunity via previous infection or vaccination, booster shots, antiviral drugs, monoclonal antibody therapies, and widely available diagnostic tests. Research to develop pan-coronavirus vaccines that could protect against multiple coronaviruses or at least multiple SARS-CoV-2 variants remains crucial.
Living with COVID is best not considered as reaching a numerical threshold for immunity, but as optimizing population protection without insurmountable restrictions in our daily lives, the authors conclude.
DM Morens et al. The concept of classical herd immunity may not apply to COVID-19. Journal of Infectious Diseases DOI: 10.1093 / infdis / jiac109 (2022).
Dr. Fauci and Dr. Mothers are available for comments.
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