The developments have some experts warning that the U.S. may be headed toward a policy of annual boosters as a sort of default position, not one arrived at by careful scrutiny of the evidence on how well vaccine protection is holding up.

“It’s alarming that there hasn’t been organization around these vital questions, so that we can actually answer them in a very enlightened and data-driven and knowledgeable manner,” said Luciana Borio, a former acting chief scientist at the FDA who is now a senior fellow for global health at the Council on Foreign Relations.

“It’s so reactive,” Borio said during a briefing for journalists organized by Georgetown University Medical Center. “And we know that this just snowballs. And we end up being stuck with decisions that don’t really make sense.”

Paul Offit, a pediatric infectious diseases clinician at Children’s Hospital of Philadelphia and a member of the FDA’s vaccine advisory panel, said there is enormous pressure mounting to move to a system of annual Covid boosters.