Herd immunity occurs when enough of a population becomes immune to a disease, either through vaccination or prior infection, that its spread becomes unlikely. For COVID-19, this concept has been central to public health strategy.
Vaccination remains the safest path to population immunity. Unlike natural infection, vaccines provide protection without the risk of severe disease, long COVID, or death.
Scientists now recognize that achieving complete herd immunity against COVID-19 may not be possible due to the virus's ability to evolve. Instead, the goal has shifted to maintaining sufficient population immunity to prevent severe outcomes and healthcare system overwhelm.