Why the FDA Paused Review of Moderna's mRNA Flu Shot

The FDA has declined to start a review of Moderna's seasonal influenza vaccine, mRNA-1010, issuing a refusal-to-file letter on February 10, 2026. The agency said the main Phase 3 study did not use the 'best-available standard of care' as the comparator, noting that a high-dose vaccine would be preferred for participants 65 and older. Moderna said the letter did not identify any safety or efficacy concerns and that the company had provided additional analyses comparing mRNA-1010 with a high-dose vaccine.

Moderna has asked for a Type A meeting with the agency to clarify the path forward, and it has submitted applications in Europe, Canada and Australia while U.S. review is paused. In 2025 the company reported positive Phase 3 results from two trials that enrolled about 43,808 people and showed higher relative vaccine efficacy than a standard-dose comparator. The U.S. Department of Health and Human Services has reduced funding for some mRNA vaccine projects, a move that has affected late-stage development and the broader regulatory environment. The company has said earliest potential approvals in other countries could arrive in late 2026 or early 2027.