Boosters for Moderna and Johnson & Johnson vaccine recipients weren’t up for debate during a C.D.C. panel.

A committee of scientific advisers to the Centers for Disease Control and Prevention voted on Thursday to recommend booster doses of the Pfizer-BioNTech coronavirus vaccine to many Americans who were fully inoculated with the same vaccine.The panel advised that those booster shots go to older Americans and people with certain medical conditions, but excluded those at risk because of their jobs.

But the panel was not asked to judge whether people who received the Moderna and Johnson & Johnson vaccines should receive Pfizer boosters. The Food and Drug Administration is reviewing data for a Moderna booster, but has not received an application from Johnson & Johnson for a booster of its vaccine.

Several experts nevertheless supported a mix-and-match strategy, and signaled that they would revisit the issue as new data emerge.

The advisers wrestled with the practicalities of endorsing a booster shot of Pfizer’s vaccine, but not the other two. Recipients of those vaccines may rightly feel resentful of being asked to wait if the evidence suggests they need boosters, they noted.

“I just don’t understand how, later this afternoon, we can say to people 65 and older, ‘You’re at risk for severe disease and death, but only half of you can protect yourselves right now,’” said Dr. Sarah Long, a pediatrician and infectious diseases expert at Drexel University College of Medicine in Pennsylvania.

“It might be the right thing to do,” she said. “It just doesn’t sound like a good public health policy.”

Some experts seemed to suggest on Wednesday that it might be better to hold off on recommending any booster shots until recipients of all three vaccines could qualify for them.

Moderna’s authorization may arrive in a few days, or weeks. The company has applied for authorization of a booster carrying half the dosage given in the first two shots, which has delayed the F.D.A.’s deliberations.

Federal regulators have indicated that there was insufficient evidence for mixing first shots of the Moderna vaccine with a Pfizer booster, or vice versa.