UPDATE 6-FDA defends its decision to refuse review of Moderna's flu vaccine

A U.S. Food and Drug Administration official on Wednesday defended the agency's surprise decision to not review Moderna's experimental flu vaccine application, saying the company should have given a higher-strength vaccine to older patients in ‌the control arm of its trial. Moderna late on Tuesday disclosed that the FDA in a letter found fault with the trial's design, sending shares of vaccine makers lower over fears this signals a tougher road ahead for those companies under this administration.

Moderna said the agency felt it should have compared its mRNA-based vaccine to the standard of care, which for older people is a high-dose flu shot, ‌not a standard shot. The mRNA technology used in Moderna's and most other COVID-19 shots credited with saving millions of lives comes with a shift in national health policy under ‌U.S. Health Secretary Robert F. Kennedy Jr., a long-time anti-vaccine activist who has been particularly critical of mRNA vaccines.

Agencies under Kennedy's purview, including the FDA and Centers for Disease Control and Prevention, have shifted from broadly assessing the safety and efficacy of vaccines and signing off on recommendations of independent experts to narrowing approvals for specific age groups and upending long-time childhood vaccine schedules. The FDA official said Kennedy was not directly or indirectly involved in the decision on the ⁠Moderna flu ​vaccine.

FDA TAKES ISSUE WITH CONTROL VACCINE The official at ⁠a press briefing said Moderna's trials, which included patients aged 50 and older, should have ensured that patients over age 65 receive the stronger flu vaccine recommended for that age group to compare with its inoculation.

"If you don't ⁠use the standard of care, guess what you're doing? You're putting seniors at risk," the official said. He said the agency was not making any determination on the vaccine itself and could consider the application ​for a younger age group were the company to resubmit.

The FDA had approved the trial design as adequate when the study was initiated 18 months earlier, a Moderna ⁠spokesperson told Reuters after the press briefing. "The industry depends on clear, transparent rules that are applied consistently in order to make the long-term investments that benefit Americans," the spokesperson said.

Moderna shares closed 3.5% down after declining as much as 12% earlier ⁠in ​the day. The FDA appears to be applying a tougher standard for comparisons and what it considers a successful outcome, Citi analyst Geoff Meacham said.

"Moderna's decision to use a standard-dose flu vaccine for its phase 3 study made sense at the time of trial design, but changes at regulatory bodies have taken place and the current sentiment towards respiratory vaccines faces a different reality." Last ⁠year, Kennedy's Department of Health and Human Services wound down mRNA vaccine development projects worth nearly $500 million under its biomedical research unit.

"I am concerned that if the next step in ⁠this process doesn't support moving forward this product ⁠to review we may have lost the mRNA platform as an option for flu or other respiratory viruses," said Dr. Demetre Daskalakis, former CDC director of the National Center for Immunization and Respiratory Diseases. Several FDA-approved flu vaccines, including those produced by AstraZeneca and Sanofi, are currently available in the ‌U.S.