Moderna thought it was walking into a standard regulatory grind. Instead, it says the FDA shut the door before the argument even started, and the reason reads like a referendum on what counts as the right comparison, at the right time, under the right administration.
What You Should Know
Moderna said the FDA sent a refusal-to-file letter for its application for an mRNA-based seasonal flu vaccine. The company says the FDA objected to the comparator used in a 40,000-person trial, despite prior FDA feedback and trial discussions.
The immediate fight is over trial design and what regulators call an “adequate and well-controlled” study. The bigger fight is about who sets the standards for mRNA vaccines in the United States, and whether those standards are being tightened in ways that reshape the market.
A Rare Procedural Hammer With Real Consequences
In a report published February 11th, 2026, CBS News said Moderna announced the FDA is refusing to consider the company’s application for a new flu vaccine made with mRNA technology.
The company said it received what is known as a refusal-to-file letter, meaning the FDA will not accept the submission for review in its current form. That is not a rejection on the merits, but it can function like one in the real world, because it pauses the clock and forces a company back into negotiation, redesign, or both.
According to CBS News, Moderna said its pivotal study enrolled roughly 40,000 people and compared the new vaccine to a standard flu shot used in current practice. Moderna said the trial found its vaccine was somewhat more effective in adults 50 and older.
The FDA, Moderna says, is focused on the baseline. It is not enough, per the letter described by CBS News, to beat a standard flu shot if the agency believes the best available standard of care in the United States at the time of the study was different for key age groups.
The Comparator Fight, Where Science Meets Strategy
CBS News reported that the refusal-to-file letter came from Dr. Vinay Prasad, the FDA’s vaccine director. Moderna said the FDA told the company the application did not contain an “adequate and well-controlled trial” because it did not compare the new shot to “the best-available standard of care in the United States at the time of the study.”
Those two phrases do a lot of work. In vaccine development, picking the comparator is not a technical footnote. It can determine whether a trial is seen as a fair test or a stacked deck, and it can determine how expensive and time-consuming the path to licensure becomes.
Moderna says the letter also points to FDA advice in 2024, under the Biden administration, that the company did not follow. However, Moderna also says that feedback included an OK to proceed with the study as planned, with a preference that a different product be used for participants 65 and older.
That is the contradiction that matters to investors, competitors, and anyone tracking how the rules shift when leadership changes. If the agency allowed a study to proceed, and then later says the comparator makes the resulting application unreviewable, companies will ask what, exactly, counts as a green light.
Moderna Says the FDA Flagged No Safety Issue
Moderna, via CBS News, framed the dispute as procedural rather than clinical. The company said the FDA did not cite safety or efficacy concerns with the product itself.
Moderna CEO Stephane Bancel said in a statement, “The FDA did not identify any safety or efficacy concerns with our product and does not further our shared goal of enhancing America’s leadership in developing innovative medicines.”
The quote is doing two things at once. It argues that the agency is not protecting patients from a bad product, and it is telling Washington, and by extension the market, that the United States risks falling behind if it treats novel vaccine platforms as guilty until proven otherwise.
Moderna said it has requested an urgent meeting with the FDA. It also noted, according to CBS News, that it has submitted for approval in Europe, Canada, and Australia.
Kennedy’s mRNA Skepticism Moves From Talking Point to Gatekeeping
CBS News framed Modernas news as part of heightened scrutiny under Health and Human Services Secretary Robert F. Kennedy Jr., who has criticized mRNA technology before and after becoming the nation’s top health official.
In the CBS News report, Kennedy is also tied to a broader policy direction: canceling more than $500 million in contracts and funding aimed at developing mRNA vaccines, particularly for respiratory viruses like coronavirus and flu.
Per CBS News, Kennedy said the Department of Health and Human Services determined that “mRNA technology poses more risk than benefits for these respiratory viruses.”
That line matters because it is not a vague caution. It is a categorical judgment, and it lands right where Modernas business model lives.
CBS News also reported that vaccine experts condemned that decision, including former Surgeon General Jerome Adams, who wrote on social media, “quite frankly, this move is going to cost lives.” Social posts do not carry the weight of a regulatory memo, but they do signal how quickly this debate becomes a public legitimacy contest.
Flu Shots Usually Move Fast, Which Is Why This Stands Out
Seasonal flu vaccines are built for speed. The CDC explains that flu viruses change constantly, and vaccines are updated to better match circulating strains each season. That reality is one reason regulators have historically allowed streamlined approaches for updating flu shots rather than rerunning massive outcome trials every year.
CBS News noted that, for decades, the FDA has allowed vaccine makers to update annual flu shots by showing they trigger an immune response. That is a very different bar than tracking who gets the flu in the real world, at scale, across a season, and then arguing about how much disease was prevented.
CBS News also reported that Prasad wrote in an internal memo last year that the streamlined method would no longer be permitted, a stance that drew backlash, including an editorial signed by more than a dozen former FDA commissioners condemning his statements.
If Modernas application is being held to a stricter standard than the industry is used to for influenza, the competitive consequences are obvious. Bigger, longer trials favor companies with deeper pockets, larger trial networks, and more tolerance for delay. They also make it harder for a new platform to break into an old market.
The Political Counterattack Is Already Here
Democrats are not treating this as a quiet technical dispute. CBS News reported that Sen. Patty Murray of Washington condemned the FDA’s decision, saying Kennedy’s team was “blocking an updated flu vaccine for no reason grounded in science.”
That is the split-screen the agency is walking into: Moderna saying there is no safety issue and that the FDA is changing the rules, and a powerful Senate voice saying the decision is politics dressed up as process. The FDA, for its part, did not immediately provide a comment to CBS News, which said it reached out to the agency.
None of this proves Moderna is entitled to approval, or that the FDA is wrong to demand a different comparator. But the procedural posture raises the stakes. A refusal-to-file letter is not a typical back-and-forth on questions, labeling, or manufacturing. It is a stop sign.
What to Watch Next
First, watch whether the FDA and Moderna agree on a path that preserves existing data, such as a bridging analysis, an additional head-to-head study in seniors, or a new trial design that meets the agency’s current view of best available care.
Second, watch global regulators. If Canada, Australia, or European authorities move forward with Modernas application while the FDA remains stuck on the comparator question, it will deepen the narrative that the United States is becoming the hardest venue for mRNA respiratory vaccines, regardless of platform performance.
Third, watch how other companies adjust. If the FDA is signaling that influenza trials must use the highest-performing licensed product as a comparator for the oldest, highest-risk cohort, every sponsor will price that into timelines, budgets, and whether to even try.
For Moderna, the message from Washington is not just about one flu shot. It is about whether mRNA, the platform that became a national project in the COVID-19 era, is now being treated as a regulatory liability.
