FDA Declines Review of Moderna's Novel mRNA Flu Vaccine Application
The United States Food and Drug Administration has formally declined to initiate a review of Moderna's approval application for its innovative mRNA-based influenza vaccine, sending the company's stock tumbling in after-hours trading. Moderna disclosed the regulatory setback in a statement released on Tuesday, revealing that the FDA's refusal was based on concerns regarding the comparative design of the company's clinical studies.
Regulatory Hurdle and Market Reaction
The FDA communicated that Moderna's application for the experimental vaccine, designated mRNA-1010, lacked an adequate comparison against what the agency considers the "best-available standard of care" for seasonal influenza. This decision triggered an immediate financial impact, with Moderna's shares plunging approximately 11 percent during extended trading sessions on Tuesday. The decline reflects investor concerns over potential delays in bringing this next-generation vaccine to market.
The specific point of contention outlined in the FDA's refusal letter, which was signed by Dr. Vinay Prasad, director of the FDA's vaccine oversight division, was the absence of an "adequate and well-controlled" study featuring a proper comparator arm. Moderna had compared its mRNA candidate to a standard-dose, already-licensed seasonal flu vaccine, but the FDA indicated this approach was insufficient for initiating a formal review process.
Moderna's Dispute and Regulatory Context
Moderna has publicly challenged the FDA's decision, stating it is inconsistent with previous written communications from the regulator. The company noted that feedback received in 2024 under the Biden administration indicated that using a standard-dose flu shot as a comparator was acceptable, though a brand specifically recommended for seniors would be preferred for participants aged 65 and older. Moderna contends the FDA allowed the study to proceed as planned based on this earlier guidance.
"This decision by the Center for Biologics Evaluation and Research, which did not identify any safety or efficacy concerns with our product, does not further our shared goal of enhancing America's leadership in developing innovative medicines," stated Moderna CEO Stephanie Bancel.
The rejection occurs against a backdrop of heightened FDA scrutiny of vaccines, particularly those utilizing mRNA technology, under the leadership of Health Secretary Robert F. Kennedy Jr. Kennedy has been openly critical of mRNA technology, and his tenure has seen regulatory actions including:
- Rolling back recommendations for COVID-19 shots
- Adding extra warnings to leading mRNA-based COVID vaccines
- Removing critics of the administration's approach from an FDA advisory panel
Path Forward and Additional Data
Despite the setback, the regulatory door remains partially open for Moderna. The company retains the option to refile its application "over protest" after meeting with FDA officials to address the cited deficiencies. Moderna has also indicated it shared additional data from a separate trial comparing mRNA-1010 to a licensed high-dose influenza vaccine used for elderly populations.
"It should not be controversial to conduct a comprehensive review of a flu vaccine submission that uses an FDA-approved vaccine as a comparator in a study that was discussed and agreed on with CBER prior to starting," Bancel argued.
This development follows broader shifts in US vaccination policy, including recent changes to childhood immunization guidelines that rolled back routine recommendations for six infectious diseases, including influenza. The intersection of evolving regulatory standards, political leadership, and innovative vaccine technology continues to shape the pharmaceutical landscape, with Moderna's experience highlighting the complex pathway for new medical products seeking approval.
