FDA Reverses Refusal-to-File on mRNA Flu Vaccine

After notifying Moderna last week that its application for review of its mRNA-1010 flu vaccine would not be reviewed for possible approval, the FDA reversed its decision based on additional discussion with and revised regulatory approach proposal from Moderna.

An mRNA vaccine trains your body to fight an infectious disease by making a small part of the virus, enabling your immune system to generate tools to prevent or lessen a future infection. Currently, only COVID-19 vaccines use mRNA technology, but both Moderna and Pfizer have developed mRNA vaccines against influenza which have been proven to be more effective than current flu vaccines.

However, after Moderna submitted an application for FDA approval of its mRNA-1010 flu vaccine, FDA notified them initially that it would not be initiating a review of the application, issuing a Refusal-to-File (RTF) letter. Moderna requested a meeting with the FDA to discuss the refusal. To advance the review, Moderna split the application by age groups, seeking full approval for adults 50 to 64 years of age and accelerated approval for adults 65 and older, along with a post-marketing requirement to conduct an additional study in older adults.

A date of August 5, 2026, has been set for availability of the vaccine if it is approved, making the mRNA-1010 available for U.S. adults 50 years of age and older, including adults 65 and older, for the 2026/2027 flu season.

Although Pfizer has not yet submitted its application for approval, it has completed a large phase 3 trial on its modRNA flu vaccine showing 34.5% higher relative efficacy than a current flu vaccine at preventing influenza A, and particularly strong responses to H1N1 and H3N2 viruses. The researchers estimated that overall effectiveness in adults over 65 could rise from the 44–54% efficacy of the 2022-23 US-licensed vaccines to about 60–67% with the modRNA formulation.

Given the FDA reversal, we would expect to see a submission for FDA review from Pfizer as well.

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