Parents vaccinated against COVID-19 shield their unvaccinated children from infection with the Alpha and Delta variants of SARS-CoV-2, according to a study of more than 150,000 households in Israel1.

More than two-thirds of Israel’s residents have received the Pfizer–BioNTech jab. To study the vaccine’s full effects, Noam Barda at Ben Gurion University of the Negev in Beersheba, Israel, and his colleagues analysed health-record data collected during two waves of COVID-19, when schools were partially closed.

Between January and March 2021, when Alpha was dominant, children under the age of 16 were around 72% less likely to get infected if they lived with two fully vaccinated parents than if they lived with two unvaccinated parents. Between July and September 2021, when Delta was dominant, children younger than 12 were 58% less likely to become infected if both parents had received a booster jab than if they had received only two vaccine doses.

The vaccines probably protected kids by reducing the risk of parents getting infected in the first place. If they did get infected, vaccinated parents were also less likely than unvaccinated parents to spread the infection to their unvaccinated children.