Yet the vast majority of the world’s population remains vulnerable to the virus, new studies found. The percentage of those infected is a small fraction of the threshold epidemiologists believe is needed for herd immunity, the point at which the virus can no longer spread widely. Some countries — notably Sweden and briefly Britain — have experimented with limited lockdowns in an effort to build up immunity in their populations.

Source: New York Times May 29, 2020 03:56 UTC