The FDA has approved Moderna’s influenza vaccine, mFlusiva, for use in adults aged 50 years and older after positive Phase III results in a trial of more than 40,000 people in this age group.
This makes Moderna the first company to get an approval for an mRNA flu vaccine from the U.S. regulator, although others are in development. This adds to the company’s two FDA approved COVID vaccines, Spikevax and mNextspike, and mResvia, an approved vaccine against lower-respiratory-tract disease caused by respiratory syncytial virus.
“The FDA approval of mFlusiva, our fourth approved product in the United States and the first mRNA-based flu vaccine, demonstrates the continued strength and versatility of our mRNA platform,” said Stéphane Bancel, chief executive officer of Moderna, in a press statement.
“Flu remains a significant public health challenge, and mFlusiva provides an important new option for America’s seniors. This approval also reflects the ongoing potential of our mRNA platform to help address important public health challenges through continued scientific innovation.”
Both Moderna and its European competitor BioNTech shot to fame during the COVID-19 pandemic as the key developers of the two most widely used vaccines, developed in record time, to protect against severe SARS-CoV-2 infection.
Although both companies have been trying to develop flu vaccines with their partners since before the pandemic, protecting against flu has proved more of a challenge.
Seasonal influenza mutates quickly and vaccines have historically targeted two A and two B lineages depending on predictions of which would be most problematic each season. Packing multiple mRNAs into lipid nanoparticles while maintaining appropriate expression, reactogenicity, and balanced immunity has proved more demanding than building a single-antigen SARS-CoV-2 vaccine.
Another challenge was that flu already has safe, inexpensive, licensed vaccines and very large studies are required to prove efficacy for a flu vaccine.
The main scientific bottleneck was achieving sufficiently strong, balanced responses to influenza B as well as influenza A. Moderna’s original formulation, like other early mRNA flu candidates, struggled on B strains.
Moderna also has a joint flu and COVID vaccine, mCombriax, approved by the European Medicines Agency earlier this year. The company also submitted this vaccine for approval by the FDA but withdrew its U.S. filing in 2025 after the FDA requested standalone-flu efficacy data. This triggered a public dispute between the company and the regulator with Moderna publishing the Refusal to File letter it received early this year online.
This week’s approval is a positive note in a period that has been a difficult one for mRNA vaccines in the U.S. with loss of research funding and pushback against the COVID-19 vaccines that are already on the market.
The mRNA flu vaccine has an advantage over the standard flu vaccine in that it is quicker to make so can respond quickly to changes in dominant flu strains. Whether the Centers for Disease Control and Prevention (CDC) advisory committee recommends mFlusiva going forward remains to be seen, however.
A recommendation by the CDC committee guides clinicians, payer coverage, and pharmacy use. If the committee declines to recommend the vaccine, or places it behind the high dose, adjuvanted and recombinant flu vaccines the CDC already prefers, coverage and demand could be lower than ideal.
