FDA Refuses to Review Moderna's mRNA Flu Vaccine After Top Official Overrules Agency Scientists

WASHINGTON — The U.S. Food and Drug Administration issued a refusal-to-file letter on Tuesday rejecting Moderna's application for the first mRNA-based seasonal flu vaccine, a decision that has exposed deep internal divisions within the agency and raised questions about whether political appointees are overriding career scientists on vaccine policy FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question..

The letter, signed by Vinay Prasad, director of the FDA's Center for Biologics Evaluation and Research (CBER), cited the lack of an "adequate and well-controlled" clinical trial. The specific objection: participants over 65 in Moderna's trial received a standard-dose flu shot as the comparator rather than a high-dose version. The CDC's Advisory Committee on Immunization Practices recommends high-dose flu vaccines for older adults when available, though standard-dose vaccines remain recommended when high-dose options are not FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question..

The Refusal-to-File Standard

A refusal-to-file is a procedural gatekeeping mechanism that allows the FDA to reject an application before substantive scientific review begins. Under FDA regulations, the agency can refuse to file a Biologics License Application if it determines the submission is insufficiently complete or the underlying studies do not meet basic regulatory standards. It is a rare and consequential step — one that effectively tells a company its data is not even worth examining FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question..

In this case, the FDA's position rests on the comparator used in the control group. For adults over 65, CDC guidance preferentially recommends high-dose flu vaccines such as Sanofi's Fluzone High-Dose, which contain four times the antigen of standard shots and have demonstrated superior efficacy in older populations with weaker immune responses. The FDA argued that using a standard-dose comparator for this age group did not reflect "the best-available standard of care in the United States" FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question..

A Timeline of Conflicting Signals

The chronology of FDA-Moderna communications makes the refusal particularly contentious. According to documents Moderna has made public, the sequence unfolded as follows:

• April 2024: CBER told Moderna in writing that using a standard-dose flu vaccine in the control group would be "acceptable," while recommending — but not requiring — a high-dose comparator for older adults FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question..
• During the trial: Moderna included details about the control group design in informed consent documents signed by all participants, a plan the company says the FDA agreed to FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question..
• February 10, 2026: Prasad signed the refusal-to-file letter, citing the very study design the agency had previously accepted FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question..

According to STAT News, career FDA scientists were prepared to review the application. David Kaslow, head of the FDA's vaccine office, wrote a detailed memo arguing in favor of proceeding with the review. Prasad overruled this recommendation — a decision confirmed by three agency officials FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question..

The FDA's Defense

Andrew Nixon, a spokesperson for the Department of Health and Human Services, said on the record that concerns about political interference were "baseless" and that "Moderna exposed participants age 65 and over to increased risk of severe illness by giving them a substandard of care against the recommendation of FDA scientists" FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question..

A senior FDA official, speaking on condition of anonymity during a press briefing on Wednesday, defended the decision more forcefully. "We told you not to run it in over 65," the official said. "You didn't do what we told you, so go back to the drawing board" FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question.. The official characterized Moderna's study design as a "brazen failure" that "raises significant ethical concerns" FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question..

The official also suggested that Moderna could resubmit a narrower application focused on the 50-to-64 age group, where the comparator question is less contentious: "It is entirely feasible that if they come back, maybe even show some humility... the review team could say: 'We'll consider that cohort'" FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question..

Moderna Pushes Back

"This was an FDA-approved trial design," said company spokesperson Chris Ridley FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question.. CEO Stéphane Bancel noted that the refusal letter "did not identify any safety or efficacy concerns" with the product US FDA declines Moderna flu vaccine review amid vaccine guidance rollbackaljazeera.com·SecondaryThe United States Food and Drug Administration (FDA) has refused to review Moderna’s application for approval of a flu vaccine, raising concerns amid a recent rollback of longstanding vaccine guidelines. In a letter to Moderna, the FDA pushed back on the Massachusetts-based biotech company’s rationale comparing its mRNA -1010, a product already on the market, to a standard dose for the seasonal flu, the company revealed on Tuesday evening.. Company president Stephen Hoge said in a subsequent interview that Moderna was "blindsided" by the decision.

Moderna reported that its mRNA-1010 vaccine was 26.6 percent more effective than GlaxoSmithKline's approved annual flu shot in clinical trials US FDA declines Moderna flu vaccine review amid vaccine guidance rollbackaljazeera.com·SecondaryThe United States Food and Drug Administration (FDA) has refused to review Moderna’s application for approval of a flu vaccine, raising concerns amid a recent rollback of longstanding vaccine guidelines. In a letter to Moderna, the FDA pushed back on the Massachusetts-based biotech company’s rationale comparing its mRNA -1010, a product already on the market, to a standard dose for the seasonal flu, the company revealed on Tuesday evening.. The vaccine is currently under review by regulators in the European Union, Canada, and Australia, with potential approvals expected in late 2026 or early 2027 US FDA declines Moderna flu vaccine review amid vaccine guidance rollbackaljazeera.com·SecondaryThe United States Food and Drug Administration (FDA) has refused to review Moderna’s application for approval of a flu vaccine, raising concerns amid a recent rollback of longstanding vaccine guidelines. In a letter to Moderna, the FDA pushed back on the Massachusetts-based biotech company’s rationale comparing its mRNA -1010, a product already on the market, to a standard dose for the seasonal flu, the company revealed on Tuesday evening..

Expert Reactions Span the Spectrum

Richard Hughes IV, a partner at Epstein Becker Green and law professor at George Washington University, called the FDA's reasoning "all pretext and obfuscation" and said it was "too risky for a manufacturer to simply run roughshod over agency guidance," making it far more likely that "this FDA turned the tables at the 11th hour" FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question..

Dorit Reiss, professor of law at UC Law San Francisco, criticized the anonymous briefing: "Not identifying yourself tells me you are unwilling to stand behind the decision because you know it is weak, flawed and untenable" FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question..

Angela Rasmussen, a virologist at the University of Saskatchewan, expressed concern that the pattern would extend beyond Moderna: "They're just coming up with reasons to not approve mRNA anything" FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question..

However, the FDA's position on high-dose comparators has scientific grounding. Geriatricians and immunologists have long noted that standard-dose flu vaccines produce weaker immune responses in older adults, and randomized trials have shown high-dose vaccines reduce influenza illness by about 24 percent more than standard-dose in people over 65. From a clinical equipoise standpoint, the FDA's argument that the control group did not receive the current standard of care has merit — even if the timing of raising this objection is what critics find indefensible.

The Broader Regulatory Landscape

The Moderna decision sits within a pattern of stricter vaccine scrutiny under the current administration. In 2025, the FDA approved COVID-19 shots from Novavax and Pfizer only for certain populations. When serious side effects emerged with a Chikungunya vaccine, the agency revoked the entire license rather than adding a warning label FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question.. The Department of Health and Human Services, under Secretary Robert F. Kennedy Jr. — who has publicly questioned vaccine safety claims — announced last year that it would scale down mRNA vaccine development and rolled back longstanding vaccine recommendations for six infectious diseases, including influenza US FDA declines Moderna flu vaccine review amid vaccine guidance rollbackaljazeera.com·SecondaryThe United States Food and Drug Administration (FDA) has refused to review Moderna’s application for approval of a flu vaccine, raising concerns amid a recent rollback of longstanding vaccine guidelines. In a letter to Moderna, the FDA pushed back on the Massachusetts-based biotech company’s rationale comparing its mRNA -1010, a product already on the market, to a standard dose for the seasonal flu, the company revealed on Tuesday evening..

The public health consequences of reduced vaccination are already visible: the United States recorded more than 2,200 measles cases in 2025, the highest in nearly three decades, with more than 730 cases reported so far in 2026 US FDA declines Moderna flu vaccine review amid vaccine guidance rollbackaljazeera.com·SecondaryThe United States Food and Drug Administration (FDA) has refused to review Moderna’s application for approval of a flu vaccine, raising concerns amid a recent rollback of longstanding vaccine guidelines. In a letter to Moderna, the FDA pushed back on the Massachusetts-based biotech company’s rationale comparing its mRNA -1010, a product already on the market, to a standard dose for the seasonal flu, the company revealed on Tuesday evening..

Investment and Innovation at Stake

The financial impact has been immediate. Moderna's shares fell sharply after the announcement, extending a decline that has seen the stock drop 29 percent in 2025 and more than 90 percent from its 2021 peak US FDA declines Moderna flu vaccine review amid vaccine guidance rollbackaljazeera.com·SecondaryThe United States Food and Drug Administration (FDA) has refused to review Moderna’s application for approval of a flu vaccine, raising concerns amid a recent rollback of longstanding vaccine guidelines. In a letter to Moderna, the FDA pushed back on the Massachusetts-based biotech company’s rationale comparing its mRNA -1010, a product already on the market, to a standard dose for the seasonal flu, the company revealed on Tuesday evening.. Citi Research analyst Geoff Meacham warned that the rejection "throws a wrench into the company's reliance on seasonal vaccines to reach its 2028 cash break-even goal" US FDA declines Moderna flu vaccine review amid vaccine guidance rollbackaljazeera.com·SecondaryThe United States Food and Drug Administration (FDA) has refused to review Moderna’s application for approval of a flu vaccine, raising concerns amid a recent rollback of longstanding vaccine guidelines. In a letter to Moderna, the FDA pushed back on the Massachusetts-based biotech company’s rationale comparing its mRNA -1010, a product already on the market, to a standard dose for the seasonal flu, the company revealed on Tuesday evening..

Bruce Y. Lee, a professor of health policy at the CUNY Graduate School of Public Health, noted that refusing to review an application removes a critical feedback mechanism for companies. "When that guidance isn't provided, it makes it very difficult for someone submitting materials to know how to proceed," he told Al Jazeera US FDA declines Moderna flu vaccine review amid vaccine guidance rollbackaljazeera.com·SecondaryThe United States Food and Drug Administration (FDA) has refused to review Moderna’s application for approval of a flu vaccine, raising concerns amid a recent rollback of longstanding vaccine guidelines. In a letter to Moderna, the FDA pushed back on the Massachusetts-based biotech company’s rationale comparing its mRNA -1010, a product already on the market, to a standard dose for the seasonal flu, the company revealed on Tuesday evening..

An mRNA flu vaccine would offer significant practical advantages: faster production than traditional egg-based vaccines, greater flexibility to respond to flu mutations, and an option for patients with egg allergies FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question..

What Happens Next

Moderna's immediate options are narrow. William Soliman, CEO of the Accreditation Council for Medical Affairs, said the company would likely need to alter its study design and resubmit US FDA declines Moderna flu vaccine review amid vaccine guidance rollbackaljazeera.com·SecondaryThe United States Food and Drug Administration (FDA) has refused to review Moderna’s application for approval of a flu vaccine, raising concerns amid a recent rollback of longstanding vaccine guidelines. In a letter to Moderna, the FDA pushed back on the Massachusetts-based biotech company’s rationale comparing its mRNA -1010, a product already on the market, to a standard dose for the seasonal flu, the company revealed on Tuesday evening.. The most probable path is a resubmission focused on the 50-to-64 age group, as the anonymous FDA official suggested.

But the longer-term question is whether the United States' regulatory posture is deterring the pharmaceutical investment needed to develop next-generation vaccines. "This is having a huge chilling effect, because no other manufacturers are going to want to make those kinds of investments," Rasmussen warned. "If you don't have access to the US market, you can't viably do business" FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question..

As Dorit Reiss put it: "Changing your position mid-stream is a problem for companies. This really will deter companies from doing vaccine trials. We need better and more influenza vaccines, not less" FDA refuses to consider Moderna flu shot in move experts claim is part of ‘anti-vaccine agenda’theguardian.com·SecondaryAgency says application rejected due to lack of ‘adequate and well controlled’ trial, but experts say ‘they’re just coming up with reasons’ A senior US Food and Drug Administration (FDA) official says Moderna’s clinical trial on a new, potentially more effective flu vaccine was a “brazen failure” and that the FDA is now calling it into question..