SARS-CoV-2: from herd immunity to hybrid immunity

Herd immunity, where a pathogen can no longer efficiently spread in a population, is achieved when a large proportion of the population becomes immune, making the spread of infection from person to person unlikely and protecting those without immunity. Despite the global spread of SARS-CoV-2, the failure of virus- and vaccine-induced immunity to prevent transmission, combined with the emergence of antigenically distinct variants, has made herd immunity to SARS-CoV-2 unachievable thus far. Where does this leave us? Herd immunity to SARS-CoV-2 has not materialized. In this Comment, David Goldblatt discusses the underlying reasons and their implications.