FDA’s Booster OK Puts Pfizer on Data Hunt, Muddles Off-Label Use

The FDA’s decision to authorize boosters on an emergency basis for a fully approved Covid-19 vaccine opens the door to rolling out more third doses while putting Pfizer Inc. on the hook for more data and complicating avenues for broader, off-label use.

Pfizer has the green light from the Food and Drug Administration to offer a single booster of its vaccine to older and high-risk populations after the agency amended the company’s emergency use authorization late Wednesday. The expanded EUA applies to those who are at least six months out of getting their second Pfizer dose. It also only applies ...