FDA's Unexpected Rejection of Moderna's mRNA Flu Vaccine Application

Moderna announced on Tuesday that the Food and Drug Administration (FDA) has declined to review its application for an mRNA flu vaccine. This decision took the renowned vaccine developer by surprise and is seen as part of a broader pattern of opposition to vaccines, especially mRNA vaccines, from an agency currently under the leadership of Robert F. Kennedy Jr., a noted anti-vaccine activist.

During his first year in office, Kennedy has significantly reduced childhood vaccine recommendations and discontinued $500 million in research funding aimed at developing mRNA vaccines for potential pandemic threats.

According to a late Tuesday news release from Moderna, the FDA's refusal was primarily due to the design of the Phase 3 trial for the mRNA flu vaccine, labeled mRNA-1010. The issue specifically stemmed from the comparator vaccine used in the trial.

The trial involved nearly 41,000 participants and cost hundreds of millions of dollars. Moderna compared mRNA-1010's safety and efficacy against licensed standard-dose influenza vaccines, including GlaxoSmithKline's Fluarix, and concluded that mRNA-1010 was superior.

Moderna stated that the FDA had reviewed and accepted the trial design on at least two previous occasions, in April 2024 and August 2025, before the company submitted the application for mRNA-1010. Additionally, they mentioned that Fluarix has been used as a comparator vaccine in past flu trials for vaccines that eventually gained approval.