The FDA recently notified Moderna that it will not examine the company’s submission for authorization of its novel influenza vaccine, which represents its inaugural use of mRNA technology for flu.
For almost two years, the FDA has been in discussions with Moderna since the firm presented Phase 3 trial results for the vaccine. Those results demonstrated the efficacy of the mRNA influenza vaccine, designated mRNA 1010.6, relative to current flu vaccines.
Moderna published on its website a chronology of its correspondence with the FDA, wherein the agency requested supplementary details on how Moderna’s vaccine performed compared to existing options for elderly individuals, who face greater risk from flu complications. The company reports it launched a Phase 3 trial in 2025 with over 40,000 participants older than 50—some receiving mRNA 1010.6, while others received the Fluarix influenza vaccine.
In the FDA’s correspondence to Moderna, which the firm posted online, the agency stated the submission “lacks sufficient completeness to permit a meaningful review.” Dr. Vinay Prasad, head of the FDA’s Center for Biologics Evaluation and Research (CBER), signed the letter and criticized the absence of data on a comparator against which Moderna’s vaccine could be measured. “CBER does not believe the submission includes a trial that is ‘adequate and well-controlled’ and consequently, the submission is inherently insufficient for review. This is due to your control group not representing the highest-quality standard of care available in the United States during the study period.”
According to reports, Prasad reached this decision contrary to the recommendations of FDA personnel, who had advised proceeding with the review and were ready to do so. This action mirrors increasing examination and constraints on vaccines under the Trump Administration; Prasad similarly disregarded FDA staff opinions when restricting annual COVID vaccines to individuals over 65 and those with compromised immune systems.
The controversy surrounding Moderna’s mRNA influenza vaccine involves correspondence from CBER to Moderna indicating that the company’s vaccine should be measured against a comparator specifically formulated for elderly populations. Moderna states the FDA never explicitly demanded modifications to the trial design.
However, FDA spokesperson Andrew Nixon stated that “the FDA declined to file Moderna’s application because the firm declined to adhere to explicit FDA guidance from 2024 requiring its product to be tested in a clinical trial against a CDC-endorsed [high-dose] influenza vaccine to compare safety and efficacy,” adding that “Moderna placed participants aged 65 and above at heightened risk of serious illness by providing them with an inferior standard of care contrary to FDA scientists’ recommendations.”
Moderna insists it supplied the necessary comparator for elderly populations. “The letter contradicts prior written correspondence from CBER to Moderna,” the firm stated. The company also noted that “CBER voiced no concerns or clinical hold remarks regarding the Phase 3 trial’s adequacy following protocol submission in April 2024 or at any point prior to the study’s commencement in September 2024.”
Moderna’s mRNA influenza vaccine is currently under review beyond the United States—in Europe, Canada, and Australia—and the company intends to file for authorization in additional nations this year as well.
The FDA’s ruling may result in individuals in other nations receiving the initial mRNA flu vaccines before Americans. A key benefit of mRNA technology is its rapid development; presently, the World Health Organization analyzes influenza data from the southern hemisphere before advising which strains appear most prevalent, and recommending them for the subsequent annual updated vaccine. This typically occurs in spring, preceding the fall and winter flu season in the northern hemisphere, encompassing the U.S. and Europe. Approximately 80% of existing flu vaccines are produced by cultivating the influenza virus in chicken eggs, necessitating months of advance preparation. Some vaccines utilize more advanced technology, such as cell-based systems, but most still employ time-consuming, decades-old techniques.
Conversely, mRNA technology requires only weeks to integrate new viral strains, as demonstrated by the swift creation of COVID vaccines targeting the most prevalent variants. mRNA-based technology could enable health authorities to react more rapidly to evolving influenza variations, and ultimately avert and guard against additional illness.
Since assuming office in January, the Trump Administration has been dismantling current vaccine policies and guidelines. Health and Human Services Secretary Robert F. Kennedy Jr., who supervises major health agencies including the FDA and CDC, has dismissed and replaced members of the CDC’s expert panel that evaluates and advises which vaccines Americans should receive. He has also eliminated recommendations for most children and adults to obtain yearly flu and COVID vaccinations. Earlier this year, HHS terminated a $590 million agreement with Moderna to create an mRNA-based avian influenza vaccine, after Kennedy announced that the government’s Biomedical Advanced Research and Development Authority, which participated in that project, would be “phasing out” mRNA vaccine development in preference for alternative platforms.
