FDA Rejects Moderna's mRNA Flu Vaccine Over Trial Design Flaws

The US Food and Drug Administration (FDA) has rejected Moderna's application to review its first mRNA seasonal flu vaccine. The decision came after regulators deemed the company's clinical trial inadequate, despite earlier feedback suggesting no major issues. Moderna now faces delays in bringing its mRNA-1010 vaccine to the US market.

The FDA refused to accept Moderna's submission, citing a trial design that failed to meet required standards. Specifically, the agency argued that the control arm did not reflect the 'best-available standard of care' for US patients. Instead of using Fluarix, a standard-dose flu vaccine, the FDA suggested Moderna should have compared its mRNA-1010 against an approved high-dose vaccine for people over 65.

Moderna's president, Dr. Stephen Hoge, expressed surprise at the decision. He stated that no concerns about the trial's design had been raised during prior discussions with the FDA. The refusal letter was signed by Dr. Vinay Prasad, an FDA official known for criticising the government's handling of Covid-19 and mRNA vaccines.

This rejection follows a broader shift in US policy. The Department of Health and Human Services (HHS) recently withdrew support for mRNA technology in infectious diseases, cancelling 22 projects worth around $500 million. While the FDA granted accelerated approval for Covid-19 mRNA vaccines during the pandemic, it has taken a stricter stance on seasonal flu vaccines. Approval decisions for these are not expected until 2026, despite submissions already made in the US, Canada, Australia, and Europe.

The FDA's decision means Moderna must now revise its trial or resubmit its application. The company's mRNA-1010 vaccine faces further delays before it can enter the US market. Regulatory hurdles for mRNA flu vaccines remain high, even as other countries move forward with reviews.