FDA Rejects Moderna's mRNA Flu Vaccine Application

The U.S. Food and Drug Administration has rejected Moderna's application to review its experimental mRNA-based seasonal flu vaccine, a decision announced by the company on Tuesday that highlights ongoing tensions over clinical trial standards for innovative vaccines. The refusal, outlined in a letter dated February 3 and signed by Dr. Vinay Prasad, director of the FDA's Center for Biologics Evaluation and Research, centers on the design of the company's Phase 3 trial, which the agency deemed not adequate and well-controlled.

Moderna's trial, launched in September 2024, involved approximately 41,000 participants worldwide, with half receiving the mRNA vaccine and the other half given a standard-dose flu vaccine, Fluarix, as a control. The study demonstrated that the mRNA vaccine was 27 percent more effective at preventing symptomatic flu cases and 49 percent more effective against hospitalization compared to the control in adults aged 50 and older. A separate trial assessed immune responses against a high-dose flu vaccine recommended for seniors. The FDA did not cite any safety or efficacy issues with the vaccine itself.

According to Moderna, the agency had approved the trial...