The FDA refuses to review the Moderna flu vaccine

Vaccine maker Moderna said Tuesday that the Food and Drug Administration has told the company that the agency will not review its mRNA flu vaccine, the latest sign of federal health policy hostile to vaccine development.

Dr. Vinay Prasad, the agency’s top vaccine regulator, rejected the company’s application for approval on the grounds that Moderna’s experimental vaccine had been compared in the clinical trial to a product the agency did not consider to be the best on the market. People in the comparison group received Fluarix Quadrivalent, a flu vaccine sold by GSK.

Moderna had spent years and hundreds of millions of dollars testing its flu vaccine, enrolling 41,000 people and targeting a market of adults 50 and older. The company concluded that its shot was superior to GSK’s product.

Dr. Stephen Hoge, the company’s president, said in an interview Tuesday that the new flu vaccine is better tailored to a single nation than those typically used by an entire hemisphere. He also said the FDA had previously signaled its support for the company’s study plan.

“This refusal to initiate a review is completely baffling to say the least,” said Dr. Hoge, adding: “It’s surprising, and we’re trying to understand what has changed.”

A spokesman for the Department of Health and Human Services, which oversees the FDA, said the agency did not comment on communications with individual drug applicants.

Moderna said it received a so-called “refuse to file” letter from the agency, meaning the company tried to submit an application for approval but it was rejected. Such superficial rejections are unusual; The agency typically conducts a thorough review before denying approval.

Moderna said the agency’s letter did not raise any specific concerns about the product’s safety or effectiveness. A journal article published last year by the company’s scientists concluded that the vaccine was safe. It was reported that some research by the company showed that the vaccine produced strong immune responses against both the A and B strains of the flu, although some results suggested that the vaccine appeared to work better against the A strain of the flu than the B strain.

A strains of flu tend to cause more flu cases and more severe illness than B strains.

This latest move by the FDA reflects the expansion of a new policy under Health and Human Services Secretary Robert F. Kennedy Jr., who has repeatedly criticized the mRNA technology used most successfully against Covid, developed by both Moderna and Pfizer. Winner of a Nobel Prize in Physiology or Medicine in 2023, the technology instructs the body to produce a fragment of a virus, which then triggers the body’s immune response.

But Mr. Kennedy has thwarted the use of mRNA in vaccines and cut hundreds of millions of dollars in funding for research using the technology, saying it is neither safe nor effective. In his first year as health minister, he canceled several projects related to the technology, including an attempt by Moderna to develop a vaccination against bird flu.

Pfizer is in a race with Moderna to develop an mRNA flu vaccine. Dr. But Marty Makary, the FDA commissioner, has been critical of Pfizer’s vaccine, saying in media interviews that it did not work in seniors in a clinical trial and suggesting it would not pass the agency’s requirements.

Moderna spent years researching a vaccine that would improve egg-based and other methods of fighting the flu, allowing countries to specifically select the strain of the virus they wanted to target.

Dr. Hoge said the company met with the FDA about the study and understood that the decision about which vaccine to use in the comparison was acceptable, although a “review issue,” he said. He said the company had requested an additional meeting with the authority over its decision to reject the application.

Blackstone, the private equity firm, invested $750 million in the development of Moderna’s flu shot, in addition to the vaccine maker’s own support for the large clinical trial, he said.

No country has approved an mRNA flu vaccine, although Mr Hoge said Moderna’s product was being tested in Europe, Canada and Australia.

In dr. Prasad’s letter to Moderna said the reason for the rejection was that the company did not conduct an “appropriate and well-controlled” study but compared its product to a flu vaccine that “does not reflect the best available standard of care.”

In recent months, Dr. Prasad imposed standards on drug companies that differed from those they expected based on previous regulatory guidance, which has sparked backlash from the biotech and pharmaceutical industries. In November, a long list of biotech investors and executives wrote a letter expressing concern about “decision volatility” and unrest at the FDA

Dr. Makary has criticized Dr. Prasad defended, saying the agency’s drug approvals last year were consistent with those of previous years.

A large clinical trial found that Pfizer’s experimental mRNA vaccine against the flu was at least as good as a comparator against A strains of the flu, but not against B strains. The study, funded by Pfizer, compared the company’s experimental vaccine with Fluzone, a vaccine marketed by Sanofi.

In an interview on “Fox & Friends” in November, Dr. Makary used Pfizer’s data, but did not name the company. “We won’t just sign off on new products that don’t work or fail in a clinical trial,” he said. “It makes science ridiculous when we just rubber-stamp things without data.”

In another interview with NPR the following month, Dr. Makary pointed out that Pfizer’s vaccine did not meet the agency’s approval criteria. “I personally like mRNA technology. But this mRNA flu vaccine failed in its randomized control trial in seniors. It showed no benefit,” he said.

He added: “Well, we basically said: We’re not interested in approving a drug that failed in its randomized Phase 3 trial.”

Pfizer said in a statement Tuesday evening that it is in discussions with health authorities about the path to approval for mRNA flu vaccines. The company declined to comment on its timeline for applying for or obtaining approval.

Perhaps no vaccine developer has been hit harder than Moderna, as federal health officials have turned against mRNA technology and some vaccines. Demand for the company’s Covid vaccine has fallen significantly after the company posted huge sales at the height of the pandemic. The FDA also restricted approval of Covid vaccinations for the season that began last fall. Moderna shares have fallen more than 90 percent since their peak in August 2021.

Moderna has said it is halting plans for late-stage trials of some experimental vaccines aimed at preventing infectious diseases and infections lurking in the body. Trials of Moderna’s late-stage experimental cancer vaccines are expected to continue unhindered.