FDA Staff Weighs In on Potential First mRNA Flu Shot

Ahead of an advisory committee meeting, FDA reviewers found no major efficacy or safety issues with Moderna’s mRNA flu vaccine candidate for adults 50 and older, potentially marking it as the first such product approved by the agency.

The trivalent mRNA vaccine (mRNA-1010) targets influenza A/H1N1, A/H3N2, and B/Victoria strains. FDA officials previously raised concerns about the study’s control arm, which used a standard-dose vaccine.

In the Fluent trial, the vaccine showed 26.6% relative efficacy in adults 50+, with 27.4% efficacy among those 65+. Compared to standard flu shots, it demonstrated superior immune response in older adults.

Reviewers questioned whether comparing mRNA vaccines to standard-dose shots is clinically relevant for seniors, where high-dose or adjuvanted vaccines are typically recommended. They also noted higher solicited adverse events (76% vs. 47%) and limited data on immunocompromised individuals or B/Victoria effectiveness.

The Vaccines and Related Biological Products Advisory Committee (VRBPAC) will vote on accelerated approval for adults 65+ on Thursday, requiring a postmarketing study. Moderna seeks approval for 50-64-year-olds without such conditions.

Despite concerns, FDA staff highlighted the vaccine’s “superior relative efficacy” and “superior immunogenicity” against high-dose comparators. Three safety points were flagged: higher solicited reactions, unspecified deaths, and potential rare events like myocarditis, requiring post-market monitoring.

mRNA technology offers advantages in updating vaccines for strain mismatches, enabling rapid reformulation compared to egg-based methods, which can delay responses to emerging flu variants.

Moderna’s path faced delays when former FDA officials criticized the trial design. After supplementary data using high-dose comparators, the review was reinstated.

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