Alliance for Pandemic Preparedness

April 9, 2021

Time-Dependent Heterogeneity Leads to Transient Suppression of the COVID-19 Epidemic, Not Herd Immunity

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  • A theoretical modeling study demonstrates how population-level heterogeneity in susceptibility to an infectious disease produces a phenomenon called “transient collective immunity”, which may lead to a temporary and misleading decrease in cases before reaching a wider and lasting herd immunity threshold. In the COVID-19 pandemic, persons highly susceptible to infection due to biological or social factors were infected early in the epidemic trajectory, removing these persons from the susceptible population, while the rest of the population were shielded from infection by stay-at-home orders. As behavioral patterns changed and previously low-risk persons became newly susceptible to higher risk of infection, subsequent waves of new diagnoses can occur.  

Tkachenko et al. (Apr 8, 2021). Time-Dependent Heterogeneity Leads to Transient Suppression of the COVID-19 Epidemic, Not Herd Immunity. Proceedings of the National Academy of Sciences. https://doi.org/10.1073/pnas.2015972118