A Food and Drug Administration advisory panel on Thursday recommended the approval of Moderna’s mRNA-based flu shot for older adults.

If approved, it would be the world’s first messenger RNA flu shot, providing public health officials with a much more nimble tool to fight influenza. In a late-stage trial, the vaccine was found to be about 27% more effective than a standard flu shot.

Despite the panel’s unanimous endorsement, questions remain about whether Americans will be able to get the vaccine, called mFlusiva, this fall. The shot must still be approved by the FDA and formally recommended by the Centers for Disease Control and Prevention’s advisory committee, which has been blocked from convening by a federal judge.

The Department of Health and Human Services, which oversees the FDA, has been hostile to mRNA technology under Health Secretary Robert F. Kennedy Jr. He’s called the mRNA Covid shot “the deadliest vaccine ever made,” and last year HHS canceled nearly $500 million in funding for mRNA vaccine research.

The path to approval of Moderna’s flu vaccine has been touch and go. Earlier this year, the FDA initially refused to even review the company’s application for the shot, before reversing course a week later.

FDA officials said the initial application was rejected because of Moderna’s decision to compare its vaccine to a standard flu shot in adults 65 and up, even though the CDC recommends this age group get a high-dose version of the vaccine. (Moderna said that the FDA had previously signed off on its trial design.)

The trial design for older adults was a robust topic of conversation during Thursday’s meeting. Ultimately, the panel — the agency’s Vaccines and Related Biological Products Advisory Committee — recommended approval for two age groups: adults 50 to 64 and adults 65 and up, with the caveat that Moderna is required to run an additional clinical trial after the vaccine reaches the market in the older group.

Hundreds of thousands of Americans are hospitalized with the flu each year, Dr. Lisa Grohskopf, the medical officer for the CDC’s flu division, told the panel Thursday. Older adults make up the majority of those cases.

There are already several flu vaccines available in the U.S., but their effectiveness can vary widely from year to year. Manufacturers must decide months in advance which strains to target, giving the virus time to evolve.

Many scientists believe mRNA technology could help solve that problem. mRNA vaccines use a small snippet of genetic code to train the body to recognize and fight the flu virus. The mRNA from the vaccine is then broken down and does not remain in the body. Because mRNA vaccines can be developed more quickly than traditional flu shots, vaccine makers may be able to update them later in the year to better match the strains that ultimately spread, said Dr. Jesse Goodman, a former FDA chief scientist and an infectious disease specialist at Georgetown University Medical Center.

During Thursday’s meeting, Moderna said that its mRNA shot requires only two to three months from strain selection to vaccine rollout, down from about six months required for traditional flu shots.

“The ability to tweak a flu vaccine later in the year than can be done with egg based vaccines may allow more up to date vaccines,” Goodman said in an email earlier this week.

After Thursday’s vote, many panel members said they liked the idea of a vaccine that could be produced more quickly and work better.

“I think that this platform adds exciting ways we can actually move our vaccines into the future,” said committee member Dr. Hayley Altman-Gans, a pediatrician at Stanford University Medical Center.

The FDA has neither a permanent vaccine chief nor a commissioner, leaving it unclear who will ultimately make the final decision on Moderna’s flu shot. Karim Mikhail, who was a senior adviser to the FDA commissioner, is now the acting head of the agency’s vaccine division following Dr. Vinay Prasad’s departure in April. Kyle Diamantas, the agency’s top food regulator, was named acting commissioner after Dr. Marty Makary’s resignation in May.

“FDA does not always follow VRBPAC, but they should be looking at the data, not sentiment, in assessing the vaccine,” said Dorit Reiss, a vaccine policy expert at the University of California Law San Francisco. “I hope the new heads of centers will make sure to do that.”

While this would be the first new mRNA vaccine approved under Kennedy, the FDA has signed off twice on yearly updates to the mRNA Covid vaccines since 2025.