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FDA Refuses to Review Moderna’s mRNA Flu Vaccine Application

The agency says the trial used the wrong comparator for seniors.

Overview

  • In a February 3 refusal-to-file letter, CBER director Vinay Prasad said Moderna’s Phase 3 data were not from an adequate, well‑controlled study because the control arm did not reflect the best available standard of care.
  • Moderna compared its vaccine to GSK’s standard-dose Fluarix in a 40,700-participant trial and says FDA had previously agreed to that plan while recommending supportive analyses versus a high-dose shot for people 65 and older, which the company submitted.
  • The company said the letter identified no safety or efficacy concerns and has requested a Type A meeting to determine the path forward.
  • An HHS spokesperson said Moderna ignored 2024 FDA guidance to use a CDC‑recommended high‑dose vaccine for seniors as the control, while multiple reports say some career FDA reviewers, including vaccine office head David Kaslow, opposed the refusal.
  • Regulatory reviews continue in the EU, Canada and Australia, and Moderna shares fell after the announcement as analysts warned the rare action could deter late‑stage investment in mRNA respiratory vaccines.