Moderna’s mRNA-based flu vaccine, mFLUSIVA, will be reviewed by a Food and Drug Administration advisory committee this week as the company seeks approval for its seasonal influenza shot. Documents released ahead of the meeting indicate that the FDA and Moderna appear to have reached alignment on key issues regarding the vaccine’s efficacy and safety.
In February, the FDA issued a refusal to file letter for Moderna's application, citing concerns about inadequate trial design. Vinay Prasad, then director of the Center for Biologics Evaluation and Research, said at that time that Moderna failed to provide an adequate and well-controlled trial. The agency specifically noted that Moderna did not use a high-dose comparator in older populations, which is considered standard of care. However, days later, the FDA reversed its decision and allowed the application to proceed with a narrowed focus on specific age groups.
Moderna is now seeking full approval for adults ages 50–64 and accelerated approval for adults 65 years and older. For those over 65, a post-marketing study will be required to secure full approval at a later date. According to documents prepared for this week’s Vaccines and Related Biological Products Advisory Committee meeting scheduled for June 18, Jefferies told investors that "the regulator appears to have softened its stance toward Moderna’s application." The FDA has found no major safety issues or imbalances in adverse events between treatment groups versus placebo. The immunogenicity data submitted were deemed supportive of efficacy in people over 65.
The studies showed superior relative vaccine efficacy compared to standard dose vaccines in patients aged 50–64 years old. The FDA document stated that "no major efficacy deficiencies were identified," with studies showing mRNA-1010 "met all prespecified sequential success criteria." Still, some uncertainties remain: available data cover only one flu season; efficacy has not been established in immunocompromised individuals or very frail older adults; safety follow-up is limited to six months; rare adverse events may not yet be apparent; higher rates of anemia and urinary tract infections were observed among those who received Moderna's shot compared with controls.
To address these concerns, Moderna proposed a bifurcated approach—seeking full approval in one age group while committing to further study in another. The advisory committee will vote on whether benefits outweigh risks for both age cohorts: adults aged 50 through 64 years old and those aged 65 years or older.
While recommendations from such committees are non-binding, they often guide final regulatory decisions. Recent changes at the agency—including increased frequency of advisory meetings following leadership changes—have brought renewed attention to these proceedings.
