Herd Immunity Already Reached in Some Regions

A non-peer-reviewed study published on October 1, 2020, says 'this model helps to explain the wide variation observed globally in seroprevalence and cumulative fatalities and raises the possibility that the proportion of people already exposed may have exceeded herd immunity threshold (HIT) in certain regions.'

This study found HIT can be lowered by the existence of a fraction of the population who are unable to transmit the SARS-CoV-2 virus, whether they are effectively segregated from the general population or mix randomly.