The FDA has approved the first flu vaccine in the United States made with messenger RNA technology, according to an announcement from manufacturer Moderna on Thursday. The decision introduces the platform used in COVID vaccines to seasonal influenza protection.

The vaccine received full approval for adults ages 50 through 64 ahead of the flu season that runs from 2026 into 2027. For adults 65 and older, the FDA granted accelerated approval.

That accelerated pathway allows the vaccine to be used while Moderna conducts an additional study to confirm its effectiveness among seniors. The differing decisions establish access for both age groups while requiring more supporting evidence for the older population.

Experts say messenger RNA vaccines can be updated more quickly in response to changes in the flu strains circulating each season. Moderna has also emphasized that ability as a central feature of the newly approved vaccine.

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The FDA based its decision on a phase 3 clinical trial involving around 40,000 participants. In that study, the new vaccine produced a 27% reduction in flu cases compared with a standard flu vaccine.

According to Moderna’s announcement, investigators identified no major safety concerns during the trial. However, the messenger RNA vaccine produced more short term side effects than conventional flu shots.

Those reported effects included arm pain, fatigue, headache and fever. The side effects were described as generally mild and temporary, according to the announcement.

Dr. Marc Siegel, Fox News senior medical analyst, said the vaccine is designed to respond quickly after the strains expected to circulate during a given year have been selected.

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"This is not a universal vaccine, but is geared for rapid turnaround once the yearly strains have been identified," Siegel said.

"It’s similar to the COVID vaccine and was found to be 25% to 30% more effective than the current flu vaccine," he added.

"It’s geared to protect the elderly."

Older adults face the greatest risk of severe influenza, according to the article. During the flu season spanning 2024 and 2025, people 65 and older accounted for 57% of hospitalizations related to flu and 71% of deaths, according to the Centers for Disease Control and Prevention.

The same season brought a substantial burden across the broader United States population. An estimated 51 million Americans contracted the flu, while the virus was linked to around 710,000 hospitalizations and 45,000 deaths, according to the Centers for Disease Control and Prevention.

The approval followed an earlier regulatory obstacle for Moderna. Earlier this year, the FDA initially refused to review the company’s application because of concerns about the design of its clinical trial, the Associated Press reported.

Moderna disputed that decision, and the FDA later agreed to proceed with its review. The process moved forward again in June, when an independent FDA advisory committee determined that the vaccine’s benefits outweighed its risks.

That committee decision helped clear the way for the FDA approval announced by Moderna. It also marked a significant step for the use of messenger RNA technology beyond the COVID vaccines that brought the platform into widespread use.

The company is now looking toward vaccines intended to cover more than one respiratory virus at a time. Moderna said the flu vaccine’s approval could help pave the way for combination vaccines offering broader seasonal coverage.

Moderna is pursuing a combined flu and COVID vaccine with the goal of allowing people to receive one seasonal shot. The company did not provide further approval details for that potential combination in the source material.

For now, the newly approved flu vaccine will be available under different FDA pathways depending on a person’s age. Adults from 50 through 64 have full approval, while those 65 and older have access through accelerated approval as Moderna completes the additional study.