Moderna shares $MRNA fell roughly 8% after the market close after the company announced that the U.S. regulator FDA declined to start a review of its application to approve the influenza vaccine mRNA-1010...

The reason was not concerns about safety or efficacy, but according to the agency an inadequately set comparator in the study—specifically the choice of comparator, which it said did not reflect the “best available standard of care.”

For the company this is an unwelcome complication because expanding the portfolio beyond COVID vaccines is supposed to be a key pillar of future growth. mRNA-1010 met primary endpoints in two late-stage trials and Moderna previously said it showed 26.6% higher efficacy than the approved GSK vaccine. Now it will have to clarify the next steps with the regulator, which could mean delays to entering the U.S. market and additional costs.

On the positive side, the vaccine remains under review in the EU, Canada and Australia, where decisions are expected around late 2026 and early 2027. For investors this is therefore not just a one-off regulatory report but a broader question: how quickly can Moderna turn its mRNA platform into new commercial products and reduce dependence on COVID-related revenues. The pace of that diversification will be key for valuation.