FDA Refuses to Review Moderna’s mRNA Flu Vaccine Application
- Food and Drug Administration (FDA) has refused to review Moderna’s application for its mRNA-based influenza vaccine, mRNA-1010, the company announced on February 10, 2026.
- According to Moderna, the FDA’s primary issue centers on the comparator vaccine used in the phase 3 trial.
- Moderna contends that this assessment is inconsistent with previous communications with CBER.
The U.S. Food and Drug Administration (FDA) has refused to review Moderna’s application for its mRNA-based influenza vaccine, mRNA-1010, the company announced on . This decision, communicated via a “refusal-to-file” (RTF) letter, does not stem from safety or efficacy concerns, but rather from questions regarding the design of the clinical trial used to support the application.
According to Moderna, the FDA’s primary issue centers on the comparator vaccine used in the phase 3 trial. The company utilized a standard-dose seasonal influenza vaccine, Fluarix, as the benchmark against which mRNA-1010 was evaluated. The FDA, in a letter signed by Vinay Prasad, MD, MPH, director of the FDA’s Center for Biologics Evaluation and Research (CBER), stated that this comparator “does not reflect the best-available standard of care.”
Moderna contends that this assessment is inconsistent with previous communications with CBER. The company asserts that CBER had approved the trial protocol, including the use of a standard-dose vaccine as a comparator, in . Upon completion of the phase 3 trial in , CBER requested and received supportive analyses regarding the comparator, indicating that the data would be considered during the biologics license application review. Moderna maintains that at no point was it informed that the comparator choice would lead to a refusal to file the application.
The FDA’s decision is considered unusual. A 2021 study indicated that RTF letters are issued in only approximately 4% of applications submitted to the agency.
Implications for mRNA Vaccine Development
The development of an mRNA-based influenza vaccine represents a potentially significant advancement in seasonal flu prevention. Traditional flu vaccines require a lengthy production process, relying on egg-based cultivation of the virus. MRNA technology offers the potential for faster production and adaptation to emerging viral strains, allowing for more timely vaccine updates. This is particularly crucial given the constant evolution of influenza viruses.
The mRNA-1010 trial data, reported last year, demonstrated a relative efficacy of 26.6% (95% CI, 16.7%-35.4%) compared to the licensed vaccine across all study participants. This efficacy was even higher among individuals aged 65 years or older. The vaccine also exhibited a safety profile comparable to existing influenza vaccines, with injection site pain being the most commonly reported adverse reaction.
However, the current regulatory hurdle raises concerns about the predictability of the approval pathway for mRNA vaccines. Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security, emphasized the importance of a stable and predictable regulatory process for encouraging investment in innovative vaccine development. “Companies need predictability if they are going to invest a billion dollars to develop a new product,” he stated. “If the regulatory pathway is subject to arbitrary changes, they will no longer be willing to make such investments.”
Broader Context of mRNA Vaccine Policy
This decision arrives amidst a shifting landscape of mRNA vaccine policy in the United States. Recent changes, including the cancellation of nearly $500 million in federal funding for mRNA vaccine development in , have raised questions about the government’s commitment to this technology. These funding cuts followed public criticism of COVID-19 mRNA vaccines and mRNA vaccine policy from Health and Human Services Secretary Robert F. Kennedy Jr. And newly appointed members of the Advisory Committee on Immunization Practices (ACIP).
While mRNA technology has proven successful in the development of COVID-19 vaccines and an approved vaccine for respiratory syncytial virus (RSV), its potential extends beyond these applications. Research is ongoing to explore the use of mRNA technology in the treatment of cancer, cystic fibrosis, and rare pediatric conditions. Expanding the mRNA platform to include an influenza vaccine could further enhance its impact on public health, particularly by enabling more rapid responses to emerging influenza strains.
Moderna has stated it is seeking a meeting with CBER officials to gain clarity on the FDA’s concerns and to determine a path forward for the mRNA-1010 application. The outcome of this discussion will be crucial not only for the future of this specific vaccine but also for the broader development and acceptance of mRNA technology in the prevention and treatment of infectious diseases.