U.S. FDA approves first mRNA flu shot from Moderna

Health Canada is still reviewing Moderna’s bid for approval of the vaccine in Canada

The U.S. Food and Drug Administration has approved Moderna's mRNA-based flu vaccine for people aged 50 and older — a complete reversal from an earlier refusal to review the shot.

The approval clears the way for the vaccine to be available in the U.S., likely next year, but won’t affect a separate, ongoing Health Canada review of Moderna’s application for approval of the same vaccine in Canada.

Nonetheless, health-care experts in Canada welcomed the development.

"The reason I think this is exceptionally good news is because the mRNA vaccines seem to be very protective of people who are older, with comorbidities, and people who are immunocompromised," said Dawn Bowdish, an immunologist and professor in the department of medicine at McMaster University in Hamilton, Ont.

The FDA approval was based on data from a late-stage trial involving more than 40,000 adults aged 50 and older, which showed the shot was 26.6 per cent more effective than existing standard-dose flu vaccines.

That’s highly meaningful for a fast-evolving respiratory disease that can be deadly to vulnerable groups such as infants or older adults, said Jason Kindrachuk, an associate professor of medical microbiology and infectious diseases at the University of Manitoba in Winnipeg and the Canada Research Chair on emerging viruses.

Moderna authorized to test vaccines to fight Ebola virus in Congo

"Something that is more efficacious is obviously going to decrease not only the toll on people's health, but also the toll on hospitals and health-care clinics across the country and certainly across the globe, which I think is a big consideration," Kindrachuk said.

The public can be “very dismissive” of the impact of influenza, Kindrachuk said, but the virus kills tens of thousands of people in the U.S. every year and thousands in Canada.

“So having something that's available, or at least an additional armament in the cupboard to be able to provide protection against something we know is going to have a public impact on an ongoing basis — that, to me, is critical.”

The shot, mFlusiva, was given a traditional approval by the FDA for adults aged 50 to 64, and an accelerated approval for those 65 years and older. Moderna has agreed to run an additional study and submit more data in adults 65 and older to confirm the vaccine's benefit in that age group.

Departure from traditional vaccines

Health experts say higher overall effectiveness, coupled with the potential for a shorter manufacturing timeline, could be game changers in fighting the flu.

Traditional flu vaccines are grown in chicken eggs, their specific makeup determined months ahead of flu season by a World Health Organization panel effectively trying to guess which flu strains will be most prominent by the time the growing process is complete.

Messenger-based RNA vaccines, which rose to prominence during the COVID-19 pandemic, give our cells instructions to build a piece of a virus protein that is harmless on its own but allows the immune system to build defences against the active virus.

mRNA vaccines proved safe and effective during COVID, review says. Cancer could be next

Health Canada authorizes mRNA vaccine trial for Ebola virus causing huge outbreak in Congo

They can also be manufactured more quickly, said McMaster’s Bowdish, “which should give us more ability to adapt to new strains as it becomes apparent which ones will affect the Northern Hemisphere.”

Scientists accelerated efforts around mRNA research with the onset of the COVID-19 pandemic — with reviews showing the billions of doses given worldwide were safe and effective — boosting efforts to use the technology against other diseases, including cancer and influenza.

Earlier this week, Health Canada authorized a clinical trial for an mRNA vaccine to fight the Bundibugyo form of the Ebola virus currently raging in the Democratic Republic of the Congo.

Flu outbreaks in Canada are rising as vaccinations lag: public health data | Hanomansing Tonight

The Moderna mRNA approval comes amid ongoing upheaval within the U.S. administration around vaccines. U.S. Health Secretary Robert F. Kennedy Jr. has been critical of vaccines, particularly those using mRNA technology, and scrutiny of vaccines at the FDA has increased since he took the role.

U.S. FDA changes course and agrees to review Moderna's mRNA flu vaccine application

Moderna’s application to the FDA for MFlusiva was refused in early February and then accepted for review a week later after Moderna made modifications to the application.

In 2025, Moderna also withdrew an application for a combo COVID-flu shot ⁠after ⁠the agency sought additional evidence demonstrating the effectiveness of its flu component.

Former FDA commissioner Marty Makary and former vaccine chief Vinay Prasad were forced to resign earlier this year amid controversies over vaccine and rare-disease drug reviews, including Moderna's flu vaccine application. Acting commissioner Kyle Diamantas has since sought to steady the agency and rebuild industry confidence.

With files from Karen Pauls, Melanie Glanz and Reuters