Several panelists said on Friday that they felt comfortable with the amount of data the N.I.H. researchers had gathered to recommend F.D.A. authorization for mixing vaccines. Dr. Ofer Levy, director of the Precision Vaccines Program at the Boston Children’s Hospital at Harvard, said that many Americans had already taken the matter into their own hands, and he urged the F.D.A. to step in.
“In the real world, all these kinds of combinations or extra boosters are already happening, so I think it’s a matter of some urgency for F.D.A. to help sort out what is admittedly a complicated and challenging scenario,” he said. “We can’t hide from it. And I do think we need to give guidance to the public.”
Dr. Amanda Cohn, a C.D.C. official, said that the F.D.A. could perhaps include general language in its authorizations of the vaccines that would allow for combinations.
“From a public health perspective, there’s a clear need in some situations for individuals to receive a different vaccine,” she said.
The N.I.H. trial looked only at antibody levels, which on their own are an insufficient measure of how well different combinations would protect people. Dr. Lyke said studies on immune cell responses were underway.
Referring to the limited data on mixing and matching, Dr. Johan Van Hoof, a Johnson & Johnson executive, said a booster was preferable. “These findings are important,” he said of the study, “but only a piece of the puzzle, and they don’t give the complete picture.”
Even so, some experts said the evidence was still pointing to switching vaccine platforms.
“At the end of the day, folks having the Johnson & Johnson should probably get an mRNA booster,” said Scott Hensley, an immunologist at the University of Pennsylvania. “It’s just a matter of how much data does the F.D.A. need before making that recommendation?
“I wouldn’t want to be in their shoes,” he added.
Todd Gregory contributed reporting.