COVID19 Graph (IMAGE)

Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign

COVID19 Graph

Caption

Epidemiological models for homogenous populations—those with little variation among individuals—predict a high value for the herd immunity threshold (HIT). For example, if the reproduction number is three, 67 percent of the population must be infected or vaccinated to reach herd immunity. With heterogeneity that remains constant over time (i.e., static levels of social activity), the HIT drops to about 42 percent. Accounting for variations in social activity over time results in an even lower threshold (~22 percent), giving the false impression that the epidemic is over when really only transient collective immunity (TCI) has been achieved. Over time, TCI wanes.

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Ahmed Elbanna

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