Herd immunity by infection is not an option

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Science  15 Jan 2021:
Vol. 371, Issue 6526, pp. 230-231
DOI: 10.1126/science.abf7921

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  • Covid-19, herd immunity and politics
    • Stephen Thomas Green, Honorary Professor/Consultant Physician, University of Sheffield, UK
    • Other Contributors:
      • Lorenzo Cladi, Associate Head of School/Lecturer in International Relations, University of Plymouth, UK

    The points made by Sridhar and Gurdasani (1) are well made.

    Seen purely from the scientific perspective, with any infectious disease “herd immunity” is acquired either through natural means – such as catching and surviving the infection – or artificial means – through, for example, a well-targeted vaccination program. For covid-19, it is vital that sufficiently high levels of herd immunity are achieved if all vulnerable groups are to be kept safe and protected from the virus. (2)

    The massive problem here is that, as with the phenomena of vaccine hesitancy and the denial of mask wearing, the phrase “herd immunity” as it applies to covid-19 has around the world taken on a political significance and potency all of its own, (3) sometimes up to very high political levels. (4-6)

    This in turn will in all likelihood have the potential to influence how the general public respond to scientifically based messages regarding how the necessary levels of herd immunity as it applies to covid-19 can be safely achieved. (7)

    Few would doubt that the example set to others by political leaders is important, and history is full of the adverse consequences of what some political leaders around the world have chosen to utter publicly – Adolf Hitler, Vladimir Lenin and Senator Joseph McCarthy all come to mind.

    Failure to do everything possible to defend people throughout the world in the face of this hideous pandemic will rightly be seen as a political...

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    Competing Interests: None declared.
  • RE: Herd Immunity Against COVID-19 Through Infection or Vaccination

    The expert authors caution against trying to achieve herd immunity through infection by COVID-19.

    Herd immunity through infection has been an unmitigated failure in Sweden in terms of high infection and mortality rates, especially for the aged, because it has not infected a sufficiently high % of the population, aka "threshold", although it has tried this strategy since the start of the pandemic.

    A recent study in Manaus, the capital of Amazonas state situated at the centre of the Brazilian Amazon, shows that herd immunity was not achieved even with an estimated threshold of 76%.

    It should be noted that the threshold is an unknown parameter, and has been discussed widely as being at least 70% or 80%, which is in the ballpark of the estimated threshold in Manaus.

    However, the duration of the estimated threshold can also be important, with the example of Sweden being a concentrated, and ultimately unsuccessful, national attempt, with approximately 50% of the infections being in the capital city of Stockholm.

    On the other hand, Manaus is an isolated city at the centre of the Brazilian Amazon, nowhere near other population centres like São Paulo, Rio de Janeiro, and the capital city of Brasilia, with the estimated threshold increasing from  66% in June 2020 to 76% in October 2020, which are not necessarily statistically significant differences.

    Since the interesting research was conducted, approved vaccines have been distribu...

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    Competing Interests: None declared.

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