Moderna ‘Shocked’ After FDA Scuttles Review of New mRNA Flu Vaccine

In a decision that “shocked” Moderna officials, the U.S. Food and Drug Administration (FDA) last week declined to review Moderna’s application for its new mRNA flu vaccine.

The FDA cited the company’s failure to perform an “adequate and well-controlled” clinical trial and its failure to use the “best-available standard of care” during the trial process.

The FDA informed Moderna of its decision in a Feb. 3 “refusal-to-file” letter, signed by Dr. Vinay Prasad, director of the agency’s Center for Biologics Evaluation and Research, which oversees vaccines, the company disclosed Tuesday.

The decision follows the FDA’s adoption of a stricter approach to approving vaccines, The Washington Post reported.

Prasad’s move to not even consider Moderna’s application, filed in December 2025, “signals a new aggressive phase to regulating drugs and forcing drugmakers to perform more rigorous studies,” Bloomberg reported.

According to Bloomberg, the FDA rarely issues refusal-to-file letters. Bloomberg cited a 2021 JAMA Internal Medicine study finding that only 4% of a sample of 2,475 applications the FDA received resulted in the issuance of such a letter.