FDA to Decide on mRNA Flu Shot That RFK Jr. Questioned
The Food and Drug Administration faces an Aug. 5 deadline to decide whether to approve Moderna’s experimental messenger RNA flu vaccine — which, if cleared, would be the first mRNA-based flu shot to reach the U.S. market. The decision is politically significant as well as scientific: Health and Human Services Secretary Robert F. Kennedy Jr., who oversees the FDA, has long questioned the value of mRNA vaccine technology, NPR reported.
Context
Messenger RNA vaccines work by instructing cells to produce a viral protein that trains the immune system to recognize a pathogen. The technology underpinned the COVID-19 shots made by Moderna and Pfizer-BioNTech — developed under the first Trump administration’s Operation Warp Speed — and is credited with saving millions of lives.
For influenza, mRNA offers a potential fix to a long-standing weakness in seasonal vaccines: traditional shots are grown in chicken eggs and take about six months to manufacture, meaning companies must choose target strains well before flu season peaks. mRNA shots can be produced faster and updated more readily to match circulating or pandemic strains, NPR explained when the FDA first rejected the vaccine.
Key Developments
The road to this week’s decision has been turbulent.
In February, the FDA sent Moderna a “refuse-to-file” letter saying it would not review the company’s application, effectively rejecting the experimental shot. The agency said Moderna’s phase 3 trial, which compared the mRNA vaccine with a standard-dose flu shot, was not “adequate and well-controlled” because a higher-potency vaccine is recommended for people 65 and older. Moderna’s president, Stephen Hoge, told NPR that the company had consulted the FDA at every step: “And they had said, you can go forward and submit and we will conduct a review.”
About a week later, the FDA reversed course after Moderna amended its application and agreed to add a confirmatory post-marketing study in older adults using a high-dose flu shot as a comparator. NPR reported that then-FDA Commissioner Marty Makary described the earlier refusal as “part of the conversation” and “a dialogue between the company and the agency.”
In June, the FDA’s Vaccines and Related Biological Products Advisory Committee voted unanimously to recommend approval for adults 50 and older, and backed accelerated approval for those 65 and older with a required follow-up study. CIDRAP reported that the phase 3 trial enrolled nearly 41,000 adults in 11 countries and found the mRNA shot offered about 27% better protection against flu-like illness than standard-dose vaccines. Moderna has proposed the brand name mFlusiva for the shot.
Analysis
The regulatory whiplash has reverberated far beyond Moderna. NPR’s reporting documented the broader political context: in August 2025, the Department of Health and Human Services announced it was terminating 22 contracts worth nearly $500 million for mRNA vaccine development under BARDA, and the administration had previously canceled a $766 million Moderna contract for a pandemic-flu vaccine.
Kennedy defended the moves, saying HHS was “moving beyond the limitations of mRNA vaccines for respiratory viruses and investing in better solutions.” Public health experts were sharply critical; Michael Osterholm, director of the University of Minnesota’s Center for Infectious Disease Research and Policy, called the funding decision “the most dangerous public health judgment” he had seen in 50 years.
The combination of funding cuts and the FDA’s initial refusal has created what researchers describe as a chilling effect on investment. “They don’t want to spend money if they don’t think there’s going to be a way to actually make money on the other end,” Rena Conti, a health economist at Boston University, told NPR. Jeff Coller, a Johns Hopkins professor who studies mRNA, added: “When you see the FDA rejecting a product that comes from Moderna, why is it that my little company would be able to push through?”
Moderna says it has invested more than $1 billion in the flu shot, including up to $750 million from Blackstone, and that it is holding off on some planned mRNA research until the regulatory landscape is clearer. In a statement to NPR, HHS said that under Kennedy’s leadership, the FDA “will continue applying rigorous, evidence-based standards to every product it reviews while supporting innovation that meets those standards.”
What’s Next
The stakes extend beyond flu. mRNA technology is also being studied for cancer and other diseases — a fact highlighted by Janusz Racz, a 69-year-old U.S. citizen in London whose lung cancer went into remission after he received an experimental mRNA cancer vaccine. Racz told NPR he wrote to Kennedy to describe his experience, saying of the administration’s actions: “And they cut off the hope.”
The FDA is expected to issue its decision by Aug. 5. If it approves the shot, Moderna says mFlusiva could be available for the 2026-27 flu season. If it does not, the decision could cement the perception that regulatory standards in the United States have become unpredictable — with consequences for the next generation of vaccines.