FDA refuses to review Moderna's mRNA flu vaccine

The Food and Drug Administration has refused to review Moderna’s application for an mRNA flu vaccine, the company revealed Tuesday.

While the move came as a surprise to the high-profile vaccine maker, it is just the latest hostility toward vaccines—and mRNA vaccines in particular—from an agency overseen by the fervent anti-vaccine activist Robert F. Kennedy Jr. In his first year in office, Kennedy has already dramatically slashed childhood vaccine recommendations and canceled $500 million in research funding for mRNA vaccines against potential pandemic threats.

In a news release late Tuesday, Moderna said it was blindsided by the FDA’s refusal, which the FDA cited as being due to the design of the company’s Phase 3 trial for its mRNA flu vaccine, dubbed mRNA-1010. Specifically, the FDA’s rejection was over the comparator vaccine Moderna used.

In the trial, which enrolled nearly 41,000 participants and cost hundreds of millions of dollars, Moderna compared the safety and efficacy of mRNA-1010 to licensed standard-dose influenza vaccines, including Fluarix, made by GlaxoSmithKline. The trial found that mRNA-1010 was superior to the comparators.

Moderna said the FDA reviewed and accepted its trial design on at least two occasions (in April 2024 and again in August 2025) before it applied for approval of mRNA-1010. It also noted that Fluarix has been used as a comparator vaccine in previous flu vaccine trials, which tested vaccines that went on to earn approval.

But in a letter dated February 3, Vinay Prasad, the FDA’s top vaccine regulator under the Trump administration, informed Moderna that the agency does not consider the trial “adequate and well-controlled” because the comparator vaccine “does not reflect the best-available standard of care.”

In its news release, Moderna noted that neither the FDA’s regulation nor its guidance to industry makes any reference to a requirement of the “best-available standard of care” in comparators.

“This decision by [the FDA’s Center for Biologics Evaluation and Research], 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 the 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 has requested a meeting with the FDA to understand the basis of the refusal. “We look forward to engaging with CBER to understand the path forward as quickly as possible so that America’s seniors, and those with underlying conditions, continue to have access to American-made innovations.”

The company noted that mRNA-1010 has already been accepted for review in the European Union, Canada, and Australia.