Has herd immunity really been achieved in some places?

By Jessica Hamzelou

Violinist Ara Malikian performs in Madrid during the pandemic

Juanjo Martin/EPA-EFE/Shutterstock

THE idea of herd immunity has had a bumpy ride as the coronavirus pandemic has played out. It was initially touted in some countries as a viable strategy for dealing with the spread of covid-19, before being dismissed. Today, some headlines celebrate the fact that many places might have achieved herd immunity including Britain and pockets of London, New York and Mumbai. But others warn that millions will die before we get there.

The true picture is far messier, partly because scientists don’t even agree on what herd …