Moderna mRNA Flu Vaccine Refusal-to-File (mRNA-1010)

Summary

On February 3, 2026, Dr. Vinay Prasad, then director of the FDA’s Center for Biologics Evaluation and Research (CBER), signed a rare refusal-to-file letter for Moderna’s mRNA influenza vaccine application (mRNA-1010, later approved under the name mFlusiva). According to reporting on the letter, Prasad told the company the FDA would not review the biologics license application because its pivotal trial was not “adequate and well-controlled” — specifically, the comparator arm, GSK’s standard-dose Fluarix, was not in his view the “best-available standard of care” for adults 65 and older.

The refusal-to-file was one of the most confrontational uses of Prasad’s gatekeeping authority during his CBER tenure. It drew coverage in both pro- and anti-Prasad outlets: critics framed it as an example of Prasad blocking vaccine approvals on novel evidentiary grounds, while supporters described it as enforcing higher trial standards on comparator choice.

The episode was short-lived as a regulatory standoff. Roughly two weeks later, the FDA reversed course and accepted the application for review. The agency’s vaccine advisory committee (VRBPAC) unanimously recommended approval in June 2026, and the FDA approved the vaccine on August 5, 2026 — after Prasad’s departure — with full approval for adults 50–64 and accelerated approval for adults 65+, conditional on a follow-up study.

Timeline

• Feb 3, 2026 — Prasad signs a refusal-to-file letter for Moderna’s mRNA-1010 BLA, rejecting review of the application over the choice of comparator in the pivotal trial.
• Mid-Feb 2026 — The FDA reverses course approximately two weeks later and accepts the application for review.
• June 2026 — VRBPAC unanimously recommends approval of the mRNA flu vaccine.
• Aug 5, 2026 — FDA approves the vaccine (marketed as mFlusiva): full approval for adults 50–64, accelerated approval for adults 65+ contingent on follow-up data — after Prasad left the agency.