Mix-and-Match Covid Boosters: Why They Just Might Work

The F.D.A. may authorize booster shots of vaccines different from the ones that Americans originally received. The science behind the move is promising.

The Food and Drug Administration seems likely to allow Americans to switch vaccines when choosing a Covid-19 booster shot. That authorization, which could come this week, is the latest development in a long-running debate over whether a mix-and-match strategy helps protect people from the coronavirus.

Here are answers to some common questions about mixing and matching booster shots.

Immunizations typically consist of two or more doses of the same vaccine. The Moderna vaccine, for example, is administered in two identical shots of mRNA, separated by four weeks.