The U.S. Food and Drug Administration has declined to review Moderna’s application for approval of its seasonal influenza vaccine, the company said on Tuesday, citing insufficient clinical evidence to support the filing.
In a letter sent to the Massachusetts based biotechnology company, the regulator said the submission did not contain “adequate and well controlled” data and concluded that the candidate vaccine did not reflect the “best available standard of care,” according to Moderna.
The application concerns mRNA 1010, an influenza vaccine developed using the same messenger RNA platform the company employed in its COVID 19 shot. Moderna said the FDA challenged its use of an already licensed standard dose flu vaccine as a comparator in clinical trials, a central element of the company’s efficacy analysis.
Chief executive Stephane Bancel said the agency’s response did not question the product’s safety profile. “The letter did not identify any safety or efficacy concerns with our product,” he said in a statement.
The FDA has not publicly detailed its reasoning beyond the assessment conveyed in the correspondence. The agency did not immediately respond to requests for comment.
Moderna previously reported that its late stage study showed the vaccine was 26.6 percent more effective than an approved influenza vaccine produced by GlaxoSmithKline. The company said the trial design had been discussed with the FDA’s Center for Biologics Evaluation and Research before the study began.
“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,” Bancel said.
Industry specialists said a refusal to review a submission typically requires additional work before resubmission. William Soliman, chief executive of the Accreditation Council for Medical Affairs, said companies in such cases generally conduct further analysis or modify trial design to meet regulatory expectations.
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“They would have to provide additional analysis or alter the study design and resubmit it for review. That’s typically how it works: they go back, address whatever the FDA is requesting, and then resubmit,” Soliman said.
Public health researchers said the absence of a full review could complicate regulatory planning. Bruce Y. Lee, a professor of health policy and management at the CUNY Graduate School of Public Health and Health Policy, said a formal review process normally clarifies deficiencies and allows developers to adjust.
“When that guidance isn’t provided, it makes it very difficult for someone submitting materials to know how to proceed,” Lee said.
The regulatory setback comes as Moderna seeks to broaden its portfolio beyond COVID 19 vaccines. In 2025 the company withdrew an application for a combined influenza and COVID vaccine to wait for efficacy data from the influenza trial now at issue.
The flu vaccine is also under evaluation by regulators in the European Union, Canada and Australia, where potential decisions are expected in late 2026 or early 2027, the company said.
The FDA action follows broader changes to U.S. vaccine policy. The Department of Health and Human Services, which oversees the FDA, announced in August that it would scale back federal support for mRNA vaccine development. The department did not respond to requests for comment on the Moderna decision.
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Health Secretary Robert F. Kennedy Jr., a long time vaccine skeptic, has overseen revisions to several immunisation recommendations, including routine vaccines for multiple infectious diseases and updates to childhood vaccination guidance.
According to U.S. public health data, more than 2,200 measles cases were reported nationwide in 2025, the highest figure in nearly three decades. More than 730 cases have been recorded so far this year.
A report by the medical publication Stat News said career scientists inside the FDA had prepared to review Moderna’s submission but were overruled by senior leadership. The agency has disputed that account, and the claims could not be independently verified.
The regulatory decision also carries financial implications for Moderna, which rose rapidly during the COVID 19 pandemic but has struggled as demand for coronavirus vaccines declined. In its November earnings report, the company posted a quarterly loss of about $200 million, with profits down $13 million from the same period a year earlier.
Analysts said seasonal vaccines are central to its long term financial plan. The FDA refusal “throws a wrench into the company’s reliance on seasonal vaccines to reach its 2028 cash break even goal,” Citi Research analyst Geoff Meacham told Reuters.
Shares of Moderna fell sharply after the announcement and were down 4.7 percent in midday trading on Wednesday. The stock has dropped about 29 percent in 2025 and remains more than 90 percent below its 2021 peak.
Moderna said it is reviewing the agency’s feedback and considering next steps. A revised submission would require additional data and a new filing before the FDA could begin a formal evaluation.