The U.S. Food and Drug Administration is refusing to consider a new mRNA flu vaccine made by Moderna, the company revealed in a statement on Tuesday.
The vaccine uses mRNA to inoculate the recipient—the same technology used in the Moderna and Pfizer coronavirus vaccines. The way these vaccines work is by delivering a copy of messenger RNA, which acts like a blueprint for cells to make proteins. In the vaccines’ case, the mRNA carries the instructions the body’s cells need to make a protein that can trigger an immune response to the targeted virus.
The FDA’s decision didn’t identify safety or efficacy concerns, according to Moderna. It was based on complaints about the studies Moderna conducted to assess the vaccine, the company said, citing a letter signed by Center for Biologics Evaluation and Research (CBER) director Vinay Prasad.
On supporting science journalism
If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
“This was a clinical trial performed with the FDA’s blessing,” says Angie Rasmussen, a virologist at the University of Saskatchewan. “The top U.S. vaccine regulator should make decisions based on a thoughtful, systematic, transparent review of the evidence that relies on diverse expertise. Based on Prasad’s refusal-to-file letter, this was not informed by any type of advisory or review process other than Prasad deciding it was insufficiently controlled.”
On a press call Wednesday, Department of Health and Human Services spokesperson Andrew Nixon said that the FDA rejected Moderna’s application “because the company refused to follow very clear FDA guidance from 2024 to test its product in a clinical trial against a CDC-recommended flu vaccine to compare safety and efficacy. 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.”
The FDA’s decision comes amid a broader campaign, spearheaded by HHS secretary Robert F. Kennedy, Jr., to remake America’s vaccine schedule. Kennedy, a long-time vaccine skeptic, has repeatedly criticized mRNA technology.
This year’s flu season has been remarkable in its severity, driven in large part by the arrival of flu variant subclade K. So far, influenza has sickened at least 22 million people in the U.S. and killed 12,000. Rasmussen notes that mRNA vaccine technology is extremely flexible and adaptable, and shots could be quickly formulated using it to help fight new virus variants like subclade K.
“If we had recognized that [subclade K] was going to be driving things, and we were using mRNA vaccines instead of conventional flu vaccine technology platforms, we would potentially be able to make an updated flu shot in time for flu season,” Rasmussen says.
This is a breaking news story and may be updated.
Additional reporting by Lauren J. Young.