The Food and Drug Administration refused to review Moderna’s application for a new influenza vaccine, the company said Tuesday, a surprise decision that could raise concerns about the agency’s posture toward drug companies and the Trump administration’s policies on vaccines.
Moderna, revealing the rejection, took the unusual step of releasing the letter it had received from Vinay Prasad, who heads the FDA’s biologics division. They also issued a strongly worded statement from its CEO Stephane Bancel, who said the decision “does not further our shared goal of enhancing America’s leadership in developing innovative medicines.”
At the heart of the dispute is what existing influenza vaccine Moderna should have used as a control when testing the efficacy of its new shot, which utilizes the same mRNA technology the company used in its Covid-19 vaccine.
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WASHINGTON, October 31, 2025 – The Food and Drug Administration (FDA) unexpectedly refused to review Moderna’s application for a novel influenza vaccine, a decision that has sparked questions about the agency’s approach to pharmaceutical companies and past vaccine policies.
A Control Group Controversy
The dispute centers on the type of existing flu vaccine Moderna should have used as a comparison when evaluating the effectiveness of its new mRNA-based shot.
Moderna disclosed the FDA’s rejection and released the agency’s letter, penned by Vinay Prasad, head of the FDA’s biologics division. CEO Stephane Bancel issued a firm statement, asserting the decision “does not further our shared goal of enhancing America’s leadership in developing innovative medicines.”
The core of the disagreement lies in the control vaccine used during Moderna’s efficacy trials. The company’s new influenza vaccine leverages the same messenger RNA (mRNA) technology that proved successful in its COVID-19 vaccine. The FDA questioned the appropriateness of the control vaccine used for comparison.
What’s a control group? In vaccine trials, a control group receives either a placebo (inactive substance) or an existing, approved vaccine. This allows researchers to compare the effectiveness of the new vaccine against a known standard or no treatment.
While the specifics of the FDA’s concerns remain largely undisclosed, the agency’s decision to not even review the application—rather than requesting additional data—is unusual and has raised eyebrows within the industry. It suggests a fundamental disagreement over the trial’s methodology.
The FDA’s decision could have broader implications, potentially influencing how other pharmaceutical companies approach the development and submission of new vaccines. Some analysts speculate the decision may reflect a shift in the agency’s posture following policy changes implemented during the Trump administration.
The situation is developing, and further details are expected as Moderna responds to the FDA’s concerns. The company has not yet indicated whether it plans to resubmit its application with revised data.
