How Many COVID-19 Booster Shots Will We Need?

Walter Barker has, since the fall of 2020, had five doses of COVID-19 vaccine. He’s already starting to ponder when he might need a sixth.

Barker, a 38-year-old office worker in New York, received his first two doses a year ago, as part of an AstraZeneca vaccine trial. But the shots, which…