FDA Panel Endorses Moderna mRNA Flu Vaccine for Ages 50 and Up but Requires Further Trial for Ages 65 and Older

An FDA advisory panel voted unanimously Thursday that the benefits of Moderna’s mRNA seasonal flu vaccine outweigh the risks for adults aged 50–64 and for adults aged 65 and older. The panel endorsed licensure via a traditional pathway for adults aged 50–64 and via an accelerated pathway for adults aged 65 and older. The FDA has committed to a decision on the licensure application by August 5.

If approved, the vaccine will be called mFlusiva. Moderna’s Phase 3 trial showed participants aged 50–64 who received the mRNA vaccine were 27 percent less likely to contract test-confirmed influenza than those who received the standard-dose comparator. Side effects were substantially higher in the mRNA arm, though most were mild and lasted one to two days.

The accelerated approval pathway for adults 65 and older requires Moderna to conduct a Phase 4 post-marketing trial comparing the vaccine to high-dose or adjuvanted vaccines. Moderna has committed to running the trial. In February, Vinay Prasad, then head of the FDA’s Center for Biologics Evaluation and Research, issued a refuse-to-file letter for the application.

Less than a week later the decision was reversed. Prasad left the FDA at the end of April. Moderna’s mRNA flu vaccine does not use eggs in its production process. mRNA vaccines can be manufactured in weeks, whereas egg-based flu vaccines take months.

The World Health Organization issues guidance in late February on the virus strains that egg-based flu vaccines should target for the following winter. The pivotal Phase 3 trial used standard-dose vaccine as the comparator rather than high-dose or adjuvanted vaccine and was conducted in 11 countries.

Wellington Sun, a former FDA employee who later worked at Moderna but is no longer with the company, spoke during the meeting’s public comment period.

David Kaslow is director of the FDA’s Office of Vaccines, Research and Review.