Moderna (NASDAQ:MRNA) shares rose 3% on Thursday, following an 11.5% gain on Wednesday, as the company’s mRNA influenza vaccine drew scrutiny from an advisory panel to the U.S. Food and Drug Administration. The advisory committee is due to vote on whether the vaccine’s benefits outweigh its risks in older adults.
The vaccine, branded mFlusiva by Moderna in its filing, is the subject of a dual-path regulatory strategy. Moderna is requesting traditional approval for adults aged 50 to 64, while seeking accelerated approval for those 65 and older. Under the accelerated pathway, approval would hinge on Moderna conducting additional post-approval studies to confirm clinical benefit.
The committee meeting follows a reversal by regulators who had initially rejected Moderna’s application. The review has also unfolded amid leadership changes at the FDA: Commissioner Marty Makary and the agency’s vaccine chief Vinay Prasad recently departed. Their exits occurred in the context of controversies tied to reviews of vaccines and drugs for rare diseases, including the company’s mRNA flu vaccine application.
Senior FDA officials have criticized aspects of Moderna’s clinical trial design. Officials said Moderna did not use the preferred higher-dose flu vaccine as the control arm for participants 65 and older, a decision senior regulators said placed patients at risk.
In briefing documents released ahead of the advisory panel meeting, FDA staff noted that data showing an immune response to Moderna’s shot could support effectiveness in adults 65 and older. At the same time, reviewers flagged specific concerns: the vaccine’s effectiveness in immunocompromised individuals, and its performance in very frail older adults who were excluded from the company’s trials.
Moderna’s own briefing material highlighted results versus standard-dose comparators. The company stated that mFlusiva outperformed standard-dose influenza shots in adults aged 50 to 64. Moderna also cited a separate, smaller study indicating the vaccine generated a strong immune response compared with a high-dose flu vaccine in adults 65 and older.
As the advisory committee prepares to vote, the review encapsulates both regulatory and clinical questions: whether immunogenicity data are sufficient to demonstrate effectiveness in the oldest cohort, how trial design choices affect risk assessments, and what additional evidence may be required if accelerated approval is granted.