Local health experts say the U.S. Food and Drug Administration’s refusal to consider Moderna’s application for a new flu vaccine made with mRNA technology is a “shock” and threatens the development of future vaccines.
The Cambridge-based company announced Tuesday that the drug regulator would not consider its application.
The news is the latest sign of the FDA’s heightened scrutiny of vaccines under Health Secretary Robert F. Kennedy Jr., particularly those using mRNA technology, which he has criticized before and after becoming the nation’s top health official. Vaccines made with mRNA technology were first made popular with the COVID-19 vaccines, are based on genetic material and generally easier and faster to produce than the traditional way.
Moderna received what’s called a “refusal-to-file” letter from the FDA that objected to how it conducted a 40,000-person clinical trial comparing its new vaccine to one of the standard flu shots used today. That trial concluded the new vaccine was somewhat more effective in adults 50 and older than that standard shot.
“It came as a shock to not just the company, but to all of us,” said Dr. Jerry Avorn, a professor of medicine at Harvard Medical School. He said the FDA’s decision came “at the very last minute, at the 11th hour, after the company had done this massive randomized trial.”
“Now everything is thrown into chaos,” he added. “This is a very unusual development.”
Experts who spoke with GBH News emphasized that the refusal to review doesn’t point to any concerns about dangers the vaccines could pose to the public.
“The FDA didn’t come out saying that there’s safety concerns, or there’s efficacy or effectiveness concerns. It’s stating that: ‘We think that we need more information,’” said Maggie Lind, an assistant professor of epidemiology at Boston University. “This is not an indication that these vaccines are dangerous or not effective or not safe. That is not the case.”
The letter from FDA vaccine director Dr. Vinay Prasad said the agency doesn’t consider the application to contain an “adequate and well-controlled trial” because it didn’t compare the new shot to “the best-available standard of care in the United States at the time of the study.” Prasad’s letter pointed to some advice FDA officials gave Moderna in 2024, under the Biden administration, which Moderna didn’t follow.
According to Moderna, that feedback said it was acceptable to use the standard-dose flu shot the company had chosen — but that another brand specifically recommended for seniors would be preferred for anyone 65 and older in the study.
Still, Moderna said the FDA agreed to let the study proceed as originally planned.
The company said it also had shared with FDA additional data from a separate trial comparing the new vaccine against a licensed high-dose shot used for seniors.
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,” Moderna CEO Stephane Bancel said in a statement.
It’s rare that FDA refuses to file an application, particularly for a new vaccine, which requires companies and FDA staff to engage in months or years of discussions.
“The government shouldn’t say your study design is acceptable — and then after the fact say, ‘But it wasn’t designed the way that we would have designed it, or that we want it to be designed,’” said Michael Ulrich, associate professor at Boston University’s School of Public Health and School of Law. “That’s a waste of time, money and resources on the part of the pharmaceutical company.”
Avorn worries the FDA’s actions will be a huge disincentive for pharmaceutical companies to invest in developing similar medications in the future.
“The fact that such a draconian and really very, very unusual decision not even to review the application can be made this late in the process is worrisome for, frankly, all drug companies — and all doctors and all patients — because it calls into question this time-honored process,” Avorn added. “[It] doesn’t mean they always get it right on either side, but that’s the rules of the road. And what’s so disturbing about this is that — as we’re seeing in many other settings, federally — the rules of the road are basically being thrown out.
“This really is a massive surprise that is not only bad for getting good flu vaccines in the future, but it’s also really a kick in the face for this very promising mRNA vaccine technology,” he added.
Moderna has requested an urgent meeting with FDA, and noted that it has applied for the vaccine’s approval in Europe, Canada and Australia.
In the last year, FDA officials working under Kennedy have rolled back recommendations around COVID-19 shots, added extra warnings to the two leading COVID vaccines — which are made with mRNA technology — and removed critics of the administration’s approach from an FDA advisory panel.
Kennedy announced last year that his department would cancel more than $500 million in contracts and funding for the development of vaccines using mRNA.
FDA for decades has allowed vaccine makers to quickly update their annual flu shots to target the latest strains by showing that they trigger an immune response in patients. That’s a far more efficient approach than running long-term studies tracking whether patients get the flu and how they fare. In an internal memo last year, Prasad wrote that the streamlined method would no longer be permitted – leading more than a dozen former FDA commissioners to pen an editorial condemning the statements.
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