Coronavirus: no certainty on herd immunity until we know more about vaccines and variants

News Snapshot:

This is the sixth in a series about China’s plans to reopen its borders amid the Covid-19 pandemic. Here, Simone McCarthy and Zhuang Pinghui look into the problems in pinning down when “herd immunity” can be achieved. Herd immunity – when enough of a population is immune to the coronavirus that its spread is limited – has been a goal of governments since the start of the Covid-19 pandemic . Now, as a handful of nations have vaccinated at least half of their population, attention has turned to questions of when herd immunity can be achieved and what it will...