“This is really significant,” says Paul Pottinger, MD, director of the Infectious Diseases and Tropical Medicine Clinic at UW Medical Center in Seattle, and cohost of the travel health podcast Germ & Worm. “It gives us not only a new choice, but also a more nimble, responsive way to help prevent flu,” he says.
Moderna is studying mFlusiva in younger age groups, but more data are needed before the FDA could expand its approval, says Dr. Pottinger.
“Since older people don’t typically respond as well to traditional flu vaccines, the idea here was to develop a shot that works better in people over 50,” says David Wohl, MD, a professor of medicine at UNC Chapel Hill in North Carolina and an infectious disease expert. Younger adults produced even stronger immune responses in earlier research, although they also had more short-term side effects after the shot, he says.
Why an mRNA Flu Vaccine Is a Big Deal
Flu vaccines have to be updated every year because influenza viruses are constantly changing. Most traditional flu vaccines are grown in chicken eggs, a process that can take six months or longer, so scientists have to choose which strains to target long before flu season begins, says Pottinger. Those decisions are informed in part by which flu viruses circulate earlier in the year in the southern hemisphere.
One advantage of that approach is speed. Moderna says mFlusiva can go from strain selection to production in about two to three months, compared with roughly six months for traditional flu vaccines, says Pottinger.
“Sometimes that means we have a mismatch between what’s actually coming in the fall and what we made in the spring,” he says. With mRNA technology, vaccine makers can select strains closer to flu season, reducing the window in which the virus can change before people are vaccinated.
