CBER Head Overruled Staff on Moderna Flu Vaccine Filing
CBER director Vinay Prasad reportedly overruled the Center’s career reviewers in deciding to issue Moderna a refusal-to-file letter (see earlier story) for its BLA for an mRNA influenza vaccine, a move that is highly unusual because these procedural decisions are typically handled by review staff, not Center leadership. In making his decision, Prasad dismissed a detailed memo from CBER Office of Vaccines Research and Review director David Kaslow recommending that the review proceed, three agency officials familiar with the letter told STAT News.
Industry observers note this marks another high‑profile instance where Prasad has intervened in vaccine regulatory decisions, contrasting with traditional FDA practice where career scientists lead product assessments. Prasad’s letter stated that the application did not contain an “adequate and well‑controlled” clinical trial because Moderna compared its vaccine against a standard-dose flu shot, which the agency said “does not reflect the best‑available standard of care in the United States at the time of the study.”
Moderna publicly criticized FDA’s decision, saying the refusal was inconsistent with previous agency feedback that the trial design was acceptable. The company highlighted that its clinical program included additional data comparing the vaccine against high-dose flu shots for older adults. Moderna has requested a meeting with FDA officials to clarify requirements for moving forward.
Industry and stakeholder reactions include concern that this regulatory stance could discourage investment in next-generation influenza vaccines, especially mRNA‑based platforms that have yet to be approved anywhere.
In a sharply worded editorial, the Wall Street Journal’s editorial board accuses Prasad of undermining medical innovation by rejecting Moderna’s application without a full review. The editorial says the agency rarely refuses to review applications — estimating roughly 4% are declined outright, typically for missing information — and argued that Moderna’s submission did not fall into that category. They questioned Prasad’s contention that the control arm should have used a high-dose flu vaccine rather than a standard-dose shot. The Journal noted that FDA officials had previously cleared the trial design and that Moderna’s vaccine demonstrated 27% greater efficacy against symptomatic flu and 49% greater protection against hospitalization compared with a standard vaccine. High-dose flu shots are generally reserved for adults over 65 in the U.S. and are not widely available in some European countries where the trial was conducted.
The editorial also drew parallels to other recent regulatory setbacks under Prasad’s watch, including the rejection of Regenxbio’s gene therapy for Hunter syndrome. The board argues that such decisions risk dampening investment in innovative vaccines and rare-disease treatments, and questions whether the White House is fully aware of the potential public health and economic consequences of the agency’s recent actions.
Meanwhile, in a 2/11 interview with FOX Business, FDA commissioner Marty Makary characterized the letter as "part of a conversation that occurs with all drug makers when they don't follow the recommendations in the guidance by the FDA. Some say that the trial that they conducted was unethical because they randomized their new mRNA flu shot in people over 65 to a worse than standard of care flu shot, an older flu shot." He said the standard of care is a high-dose flu shot, which FDA had recommended Moderna use.
"So they're going to probably come back... and file the application," he continued. "Perhaps they'll break it up into two subgroups based on the age categories. But this is the normal back-and-forth dialog that the FDA has with companies, especially when they don't follow the guidance."