The U.S. Food and Drug Administration (FDA) has refused to accept an application from Moderna for its mRNA-based seasonal flu vaccine, marking a significant setback for the company’s efforts to expand its mRNA technology beyond COVID-19. The application was rejected due to concerns over the design of the clinical trial, the company said Tuesday.
FDA Rejects Moderna’s mRNA Flu Vaccine Application
The FDA rejected Moderna’s request to review its experimental mRNA flu vaccine, stating that the clinical trial did not include an “adequate and well-controlled” control group. Specifically, the control arm did not meet the “best-available standard of care” in the U.S. at the time of the study. Despite this, the FDA did not express concerns about the vaccine’s safety or efficacy.
Moderna expressed surprise at the rejection, claiming that the agency had previously approved the trial design. Dr. Stephen Hoge, president of Moderna, said the company was not informed that its trial design was inadequate before submitting the application.
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According to the FDA, Moderna failed to test the vaccine against the CDC-recommended flu vaccine, which the agency had suggested in a 2024 guidance. The FDA stated that Moderna’s refusal to comply with the guidance led to the rejection.
Controversy Within the FDA
The decision has sparked internal disagreements at the FDA. Dr. David Kaslow, who heads the FDA’s vaccine office, reportedly supported the review process and was in favor of advancing the application. However, Dr. Vinay Prasad, director of the FDA’s Center for Biologics Evaluation and Research, signed the refusal letter, a rare and highly unusual move.
Despite the division within the agency, the FDA remains focused on ensuring that vaccines meet rigorous standards for safety and efficacy.
Moderna’s Response and Future Plans
Moderna has requested a meeting with FDA officials to understand how to proceed with its application. Meanwhile, the company continues to move forward with the development of an mRNA combination flu and COVID-19 vaccine in other countries, including Europe.
“We do expect our first approval for the combination vaccine in Europe, probably this year,” said Dr. Hoge. “That will be a milestone event for us.”
Moderna had hoped to advance its mRNA flu vaccine application in the U.S. to move forward with the combined flu and COVID-19 vaccine. With the FDA review now on hold, the company faces a setback but remains optimistic about its prospects internationally.
