WASHINGTON — The Food and Drug Administration, under the leadership of Vinay Prasad, has refused to review Moderna’s application for a new influenza vaccine, a decision that overruled the agency’s internal scientific reviewers. The move, reported by STAT News, signals a deepening trend of stricter vaccine scrutiny at the FDA and raises questions about the future of mRNA-based flu vaccine development.
According to three agency officials familiar with the matter, the team of career scientists was prepared to initiate a review of Moderna’s application. David Kaslow, head of the FDA’s vaccine office, reportedly authored a detailed memo recommending the agency proceed with the evaluation. Prasad, however, overruled this recommendation, effectively halting the review process.
The rejection centers not on safety or efficacy concerns – Moderna stated the FDA did not raise any – but on the “comparator” used in the company’s clinical trial. The FDA argued that using the standard flu shot as a benchmark against which to measure the effectiveness of Moderna’s mRNA vaccine “does not reflect the best-available standard of care.” Moderna countered that this reasoning is “inconsistent” with prior guidance received from the agency in 2024 and 2025, and that the use of an FDA-approved vaccine as a comparator should not be controversial.
This decision arrives amidst growing concerns about a shift in the FDA’s approach to vaccine approvals. Health Secretary Robert F. Kennedy Jr., a known vaccine critic, has been in office since , and his influence is increasingly apparent. Prasad and another top official, Tracy Beth Høeg, have already taken steps to exert greater control over vaccine surveillance, wresting authority from career civil servants, according to STAT News reporting from November .
The implications of this decision extend beyond Moderna. Shares of the company fell nearly 7% on Wednesday, , reflecting investor anxieties about the regulatory pathway for the vaccine and the broader implications for the company’s pipeline. The rejection also casts a shadow over the future of mRNA technology in the influenza vaccine market. Moderna’s vaccine, based on the same mRNA platform as its successful COVID-19 shot, demonstrated 26.6% greater effectiveness than the standard flu shot in a Phase 3 clinical trial last year.
The FDA’s stance is particularly noteworthy given the ongoing need for improved influenza vaccines. The standard flu shot’s effectiveness varies significantly from year to year, often falling short of expectations due to viral mutations. An mRNA-based vaccine, with its potential for rapid adaptation to new strains, could offer a significant advantage. However, the current regulatory environment appears to be creating hurdles for such innovations.
The Department of Health and Human Services, which oversees the FDA, offered a limited response, stating through a spokesperson that the agency generally does not comment on regulatory communications with individual sponsors. This lack of transparency further fuels concerns about the decision-making process within the FDA.
The situation highlights a broader tension between the traditional regulatory approach and the potential of novel vaccine technologies. While the FDA’s mandate is to ensure the safety and efficacy of medical products, critics argue that overly stringent requirements or inconsistent application of standards can stifle innovation and delay access to potentially life-saving treatments. The rejection of Moderna’s application, and the circumstances surrounding it, are likely to intensify this debate.
The FDA’s decision also raises questions about the agency’s commitment to fostering a predictable and transparent regulatory environment for vaccine developers. Uncertainty about the review process can discourage investment in new technologies and ultimately hinder efforts to improve public health. The coming months will be crucial in determining whether this represents a temporary setback or a fundamental shift in the FDA’s approach to vaccine regulation.
