The Food and Drug Administration on Wednesday approved mFlusiva, Moderna's mRNA-based influenza vaccine and the first flu shot cleared in the United States to use the messenger-RNA platform that powered the Covid vaccines.
The clearance covers adults 50 to 64 in full and adults 65 and older on accelerated approval, and it lands in a regulatory limbo that could keep the shot out of many pharmacy chairs even after Moderna delivers doses for the 2026-27 flu season. Private insurers generally cover only vaccines that the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices recommends, and a federal judge has blocked that panel from convening.
The trial
In a late-stage trial of more than 40,000 older adults across 11 countries, mFlusiva proved about 27 percent more effective than a standard flu shot, Moderna said. Traditional flu shots range in effectiveness from 22 percent to 56 percent, according to the Mayo Clinic. Injection-site pain, fatigue and headaches were more common among mFlusiva recipients but mild to moderate. Moderna said it takes two to three months from picking a strain to shipping doses, compared with about six months for existing vaccines.
"If you’re choosing the strain half a year before, how good can we be at sharpshooting?" said Dr. Ofer Levy, director of the Precision Vaccines Program at Boston Children's Hospital.
Regulatory whiplash
The approval came despite the FDA's earlier refusal this year to review Moderna's application. Vaccine director Vinay Prasad faulted the 40,000-person study for comparing mFlusiva against a standard flu shot rather than the high-dose formulation the CDC recommends for people 65 and older. The agency reversed course about a week later after discussions "led to a revised regulatory approach and an amended application, which FDA accepted." Moderna agreed to run an additional study in the older group. In June, the FDA's independent vaccine advisory committee unanimously recommended approval.
The counterpoint
Health and Human Services Secretary Robert F. Kennedy Jr., an anti-vaccine activist, has called the Covid mRNA shots "the deadliest vaccine ever made" and canceled nearly $500 million in mRNA vaccine research funding under HHS last year, according to NBC News. Kennedy had not publicly responded to Wednesday's decision by press time, and today's reporting on the approval drew only from left-of-center outlets. No industry-skeptic or administration source addressed the clearance on the record.
Moderna said mFlusiva will be available for the 2026-27 flu season. Without an ACIP recommendation, private insurance coverage will be limited and federal programs including Vaccines for Children and Medicaid will lack guidance on distribution. "That is a serious concern," Levy said.