A panel of expert advisers to the Food and Drug Administration voted unanimously Thursday to recommend that the COVID-19 vaccine be updated to target emerging subvariants of omicron.

The COVID shot that's currently available is known as a "bivalent" vaccine because it was tailored to target both the original strain of the coronavirus and the omicron subvariants that dominated last winter.

But the FDA panel recommended that drugmakers abandon the bivalent design and instead move to a "monovalent" vaccine that only targets omicron subvariants. The idea is to roll out the newly formulated shots in anticipation of a possible uptick in cases this fall.

The committee specifically supported targeting the subvariant XBB.1.5, which accounts for about 40% of new infections in the U.S.

In an analysis, FDA scientists said data from vaccine manufacturers indicate that an updated monovalent formulation that targets XBB subvariants "elicits stronger neutralizing antibody responses" against XBB strains than current bivalent vaccines.

"There doesn't seem to be any particular advantage to a bivalent vaccine," said Dr. Eric Rubin, a professor of immunology and infectious diseases at Harvard who is also a member of the advisory committee.

While there was wide agreement about moving to a monovalent vaccine, there was considerable debate among committee members over whether the COVID-19 vaccine should be handled like the influenza vaccine, which is revamped every year in anticipation of flu season.

"People understand a yearly influenza vaccine," said Dr. Peter Marks, director of the FDA's Center for Biologics Evaluation and Research. "At this point it may not be yearly, but, for all intents and purposes, it looks like by next fall there will be further drift from this [strain] and we may have to come back here."

But some worried that drawing too close a parallel to influezna could actually lead to confusion among Americans.

"This is not the flu," said committee member Dr. Paul Offit, a professor of pediatrics at the Children's Hospital of Philadelphia. He pointed out that many Americans already have some protection against severe illness from COVID-19 because of prior infection, vaccination, or both.

"I'm all for updating this vaccine, but I think we need to define... who really benefits from booster dosing? Because it's not everybody," he said.

It's not yet clear who federal officials will recommend should get the updated omicron vaccine.

During the meeting, the CDC shared data that shows that, since last April, COVID hospitalizations and deaths have been low in most groups. But they have been disproportionately high in people who are 75 or older, suggesting this group might need extra protection. Those with health issues like chronic lung disease or diabetes might also have higher risks.

The FDA is now going to consider the committee's discussion and will likely issue an official recommendation about the vaccine formulation within a few days, which will give vaccine makers a path to follow.

If all goes according to plan, it's expected the new vaccines should be out in the fall – by around late September or early October.