Impact of host resistance on cumulative mortality and herd immunity threshold for SARS-CoV-2

Jose Lourenco, Francesco Pinotti, Craig Thompson, Sunetra Gupta

doi: https://doi.org/10.1101/2020.07.15.20154294

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Abstract

It is widely believed that the herd immunity threshold (HIT) required to prevent a resurgence of SARS-CoV-2 is in excess of 50% for any epidemiological setting. Here, we demonstrate that HIT may be greatly reduced if a fraction of the population is unable to transmit the virus due to innate resistance or cross-protection from exposure to seasonal coronaviruses. The drop in HIT is proportional to the fraction of the population resistant only when that fraction is effectively segregated from the general population; however, when mixing is random, the drop in HIT is more precipitous. Significant reductions in expected mortality can also be observed in settings where a fraction of the population is resistant to infection. These results help to explain the large degree of regional variation observed in seroprevalence and cumulative deaths and suggest that sufficient herd-immunity may already be in place to substantially mitigate a potential second wave.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

Nothing to declare.

Author Declarations

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

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https://www.medrxiv.org/content/10.1101/2020.07.15.20154294v1