The US Food and Drug Administration is considering whether to approve Moderna’s mRNA flu vaccine, mFlusiva, which could become the first licensed seasonal influenza vaccine using this technology. The decision matters because it would expand mRNA beyond Covid-19 vaccines and comes amid heightened federal scrutiny of the technology by Health Secretary Robert F. Kennedy Jr., who has questioned it.

The FDA is expected to decide by 5 August, after its vaccine advisory panel voted unanimously in June that the vaccine’s benefits outweighed its risks for adults aged 50 and over. In a trial of roughly 40,000 people, flu-like illness occurred in 2.0% of mRNA-vaccine recipients, compared with 2.8% receiving a standard-dose flu vaccine — a relative efficacy improvement of 26.6%. The application was initially rejected over the choice of comparator vaccine for older adults, before the FDA agreed to review it under a plan for full approval in people aged 50–64 and accelerated approval for those 65 and over.