Moderna says FDA refuses to review application for flu shot

The Food and Drug Administration has refused to start a review of Moderna‘s application for its experimental flu shot, the company announced Tuesday, in another sign of the Trump administration’s influence on tightening vaccine regulations in the U.S. 

The company’s stock fell roughly 7% in after-hours trading Tuesday.

Moderna said the move is inconsistent with previous feedback from the agency from before it submitted the application and started phase three trials on the shot, called mRNA-1010. The drugmaker said it has requested a meeting with the FDA to “understand the path forward.” 

Moderna noted that the agency did not identify any specific safety or efficacy issues with the vaccine, but instead objected to the study design, despite previously approving it. The company added that the move won’t impact its 2026 financial guidance.

Moderna’s jab showed positive phase three data last year, meeting all of the trial goals. At the time, Moderna said the stand-alone flu shot was key to its efforts to advance a combination vaccine targeting both influenza and Covid-19.

The announcement follows sweeping changes to U.S. immunization policy over the past year under Health and Human Services Secretary Robert F. Kennedy Jr., a prominent vaccine skeptic. 

Moderna on Tuesday specifically pointed to the FDA’s top vaccine regulator, Vinay Prasad, who returned to the agency in August after being ousted. Prasad, who heads the agency’s Center for Biologics Evaluation and Research, or CBER, has been vocal about tightening regulations for vaccines and recently linked child deaths to Covid shots. 

In a letter signed by Prasad on Feb. 3, he said the sole reason why the FDA refused to review the application was because of how the clinical trial on the shot was designed.

The agency specifically took issue with Moderna’s decision to compare its product to a standard, approved flu shot, arguing that it “does not reflect the best-available standard of care.” As a result, the FDA said the study did not meet its definition of an “adequate and well-controlled” trial.

Moderna disputes that reasoning, noting that FDA rules and guidance do not actually require trials to use the most advanced or highest-dose vaccine as a comparator in clinical studies. 

“This decision by CBER, which did not identify any safety or efficacy concerns with our product, does not further our shared goal of enhancing America’s leadership in developing innovative medicines,” Moderna CEO Stéphane Bancel said in a release. “It should not be controversial to conduct a comprehensive review of a flu vaccine submission that uses an FDA-approved vaccine as a comparator in a study that was discussed and agreed on with CBER prior to starting.”

Moderna said it expects the earliest approval for its flu shot to be in late 2026 or late 2027, pending regulatory reviews in the U.S., Europe, Canada and Australia.

The FDA said it does not comment on regulatory communications to individual sponsors.