FDA Won’t Review Moderna Application For First mRNA-Based Flu Vaccine
The Food and Drug Administration has declined to review Moderna’s application for the first mRNA-based flu vaccine, a decision that shocked the company and that comes as the agency plans to tighten federal vaccine approvals.
The nation’s top vaccine regulator, Vinay Prasad, told Moderna that it lacked an “adequate and well-controlled” study, the company said in a news release Tuesday. In a large clinical trial, the vaccine was compared with Fluarix, an approved standard-dose flu vaccine. Prasad’s letter did not detail concerns with the safety or efficacy of the vaccine, which Moderna was aiming to target for adults ages 50 and older.
Moderna President Stephen Hoge said that the company had previously engaged with the FDA on the trial design and that the agency had indicated it would be acceptable.
“We’re trying right now to reach out to the FDA and understand what would be necessary for them to start reviewing the submission,” Hoge said in an interview.
Companies conduct clinical trials with the oversight of the FDA, which offers feedback on the design of the trials. Moderna indicated that in April 2024, the FDA provided feedback saying the agency agreed Moderna’s trial design was “acceptable,” though it recommended that the investigational drug be compared against a higher-dose flu shot for those 65 and older.
Andrew Nixon, a spokesman for the Department of Health and Human Services, said in a statement Wednesday that the application was rejected because “the company refused to follow very clear FDA guidance from 2024.”
“Moderna exposed participants aged 65 and over to increased risk of severe illness by giving them a substandard of care against the recommendation of FDA career scientists,” Nixon said. “The most protective flu shots for seniors are a subset of high dose flu shots.”
Last fall, Prasad laid out a stricter approach for federal vaccine approvals, alarming a dozen former FDA leaders who said the change risks undermining the nation’s ability to fight diseases. In a November internal email, Prasad urged the agency to rethink its framework for annual flu shots, examine whether Americans should receive multiple vaccines at the same time and require larger studies to net approval for certain shots.
Moderna has requested a formal meeting with the agency. It said the vaccine has been accepted for review in the European Union, Canada and Australia.
Several vaccine experts said the decision raises questions for vaccine-makers about shifting guidance from the FDA, which could deter future investments in expensive clinical trials.
Jesse Goodman, one of Prasad’s predecessors as head of the agency’s Center for Biologics Evaluation and Research, said Moderna’s vaccine appeared “promising.” He questioned why the FDA would not go forward with a full review, identify any gaps in the data and have a public discussion about the vaccines.
MRNA technology was lauded during the covid-19 pandemic for being developed at record speed and saving millions of lives. President Donald Trump in his first term called mRNA vaccines a “modern-day miracle.”
Leaders in the Trump administration’s second term, however, have expressed broader skepticism of mRNA technology, chilling the vaccine industry that has been researching the technology’s possible use for cancer, other diseases and future pandemics. In August, HHS announced the “wind-down” of $500 million in mRNA projects supported by the Biomedical Advanced Research and Development Authority (BARDA), the government’s biodefense agency. Last May, the agency pulled funds for Moderna to develop a vaccine against bird flu.
“We’re moving beyond the limitations of mRNA and investing in better solutions,” Health Secretary Robert F. Kennedy Jr. said in a statement when the mass termination of mRNA projects was announced in August.
A senior FDA official, who spoke on the condition of anonymity under ground rules set by HHS, told reporters that Kennedy was not involved in, nor was he informed in advance, of the Moderna decision. The official declined to predict the next steps.
In January, at the World Economic Forum in Davos, Switzerland, Moderna’s chief executive, Stéphane Bancel, told Bloomberg TV that the company would stop investing in late-stage vaccine trials that are a crucial part of the approval process.
“You cannot make a return on investment if you don’t have access to the U.S. market,” Bancel said.
Moderna conducted two late-stage, “Phase 3” trials (one of the final steps before seeking drug approval) designed to test the safety and effectiveness of its mRNA flu vaccine, enrolling more than 43,000 adults age 50 or older. In one trial, more than 40,000 participants received either a dose of the experimental mRNA flu vaccine or a standard dose of an existing flu shot. In another, participants received a dose of the mRNA vaccine, a standard shot or a high-dose influenza shot recommended for adults 65 and older.
Moderna said the FDA notified the company of its decision on Feb. 3 in a “refusal to file” letter stating that the company’s application was, “on its face, inadequate for review.”
Refuse-to-file letters are infrequently used by U.S. regulators, according to a study published in JAMA Internal Medicine. Over a decade, that study found, only 4 percent of nearly 2,500 applications received such letters.
(c) 2026, The Washington Post
