The U.S. Food and Drug Administration (FDA) has refused to consider Moderna’s application for a new flu vaccine, which utilizes Nobel Prize-winning mRNA technology, the company announced on Tuesday.
This decision signals heightened scrutiny of vaccines by the FDA under Health Secretary Robert F. Kennedy Jr., particularly those employing mRNA technology, which he has publicly criticized both before and since assuming his role.
Moderna received a “refusal-to-file” letter from the agency, which raised objections to the methodology of its 40,000-person clinical trial. The trial had concluded that Moderna’s new vaccine was somewhat more effective in adults 50 and older than the standard shot it was compared against.
However, Dr. Vinay Prasad, the FDA vaccine director, stated in his letter that the application did not contain an “adequate and well-controlled trial” because it failed to compare the new jab to “the best-available standard of care in the United States at the time of the study.” Prasad’s communication also highlighted advice given to Moderna by FDA officials in 2024, under the Biden administration, which the company reportedly did not follow.
According to Moderna, that feedback said it was acceptable to use the standard-dose flu shot the company had chosen — but that another brand specifically recommended for seniors would be preferred for anyone 65 and older in the study. Still, Moderna said, the FDA did agree to let the study proceed as originally planned.
The company said it had shared with the FDA additional data from a separate trial comparing the new vaccine against a licensed high-dose shot used for seniors.
The FDA “did not identify any safety or efficacy concerns with our product” and “does not further our shared goal of enhancing America’s leadership in developing innovative medicines,” Moderna CEO Stephane Bancel said in a statement.
The FDA rarely refuses to file an application, particularly for a new vaccine, which requires companies and FDA staff to engage in months or years of discussions.
Moderna has requested an urgent meeting with the FDA, and noted that it has applied for the vaccine’s approval in Europe, Canada and Australia.
In the last year, FDA officials working under Kennedy have rolled back recommendations around COVID-19 shots, added extra warnings to the two leading COVID vaccines — which are made with mRNA technology — and removed critics of the administration’s approach from an FDA advisory panel.
Kennedy announced last year that his department would cancel more than $500 million in contracts and funding for the development of vaccines using mRNA.
The FDA, for decades, has allowed vaccine makers to quickly update their annual flu shots to target the latest strains by showing that they trigger an immune response in patients. That’s a far more efficient approach than running long-term studies tracking whether patients get the flu and how they fare. In an internal memo last year, Prasad wrote that the streamlined method would no longer be permitted, leading more than a dozen former FDA commissioners to pen an editorial condemning the statements.
