US experts wrestle with how to update COVID-19 vaccines

More than two years into the COVID-19 pandemic, U.S. health officials are beginning to grapple with how to keep the vaccines updated to best protect Americans from the ever-changing coronavirus. On Wednesday, a panel of vaccine advisers to the Food and Drug Administration spent hours debating key questions for revamping the shots and conducting future booster campaigns. They didn’t reach any firm conclusions. The questions facing the experts included: How often to update the vaccines against new strains, how effective they should be to warrant approval and whether updates should be coordinated with global health authorities. Last week, the FDA authorized a fourth dose of the Pfizer or Moderna vaccines for anyone 50 or older and for some younger people with severely weakened immune systems. It’s an effort to get ahead of another possible surge.