According to their new mathematical model, far less people need to be infected with COVID-19 in order to reach herd immunity levels.
That model, which was specially designed just for this study, categorizes people into different groups based on age and social activity levels. Once those factors are incorporated into herd immunity projections, the percentage of a population that would have to become immune drops from 60% to 43%.
However, the study’s authors caution their calculations are not exact; that 43% number should not be looked at as an exact value, or even the best possible estimate.
The authors also note that people who are more socially active are more likely to be infected with COVID-19. Similarly, they are more likely to pass the virus on to others.
original study in Science: https://science.sciencemag.org/content/early/2020/06/22/science.abc6810