Children, for example, are far less likely than adults to become severely ill from Covid-19. And there is a risk, though it is rare, of vaccine-related myocarditis (inflammation of the heart) which is more common in younger people, in particular boys, after their second dose of an mRNA vaccine. Some countries like Norway and Britain give only one dose of the Pfizer vaccine to children age 12 to 15 to avoid potential risks like myocarditis from the second dose.

But giving a single dose to all children comes with concerns that one dose might not provide strong and long-lasting protection. Whether a child has had Covid-19 or not isn’t a part of these vaccination decisions — and should be.

If scientists and policymakers consider the power of hybrid immunity, it’s reasonable to recommend a single dose for children without serious health problems who have had Covid-19. If parents are unsure if their children have been previously infected, antibody tests could be given when they get their first vaccine dose. Although these tests may not pick up all children who have had Covid-19, they would pick up most, and only children without confirmed infection could be called back for a second dose. Such an approach could also help free up doses for the many other countries with low vaccine supply and at-risk adults who haven’t been vaccinated. The approach should at least be considered for further study.