Moderna's mRNA Flu Shot Outperforms Standard Vaccine by 27%

Getting a flu shot every year matters, but some seasons they only reduce illness by 20% to 30%. A new type of vaccine could change that for millions of people.

Moderna's mRNA flu vaccine just proved itself in a major trial involving over 40,000 adults ages 50 and up across 11 countries. The results, published in the New England Journal of Medicine, show the mRNA shot performed 27% better than standard flu vaccines during the 2024-2025 flu season.

The numbers tell a promising story. Only 2% of people who received the mRNA vaccine got sick, compared to 2.8% in the standard flu shot group. While side effects like fatigue and arm pain were slightly more common with the mRNA shot, they were mild and temporary.

The real game changer isn't just effectiveness. It's speed.

Traditional flu shots take months to produce, forcing health officials to guess which flu strains will circulate up to 12 months before peak season. That long lead time can result in mismatched vaccines when new strains emerge unexpectedly, like last summer's H3N2 subclade K variant.

mRNA vaccines can be manufactured much faster, giving officials more time to make strain selections and allowing manufacturers to pivot if viruses change. "The ability to make vaccine in shorter time periods may help better match new vaccines to emerging influenza viruses," said Dr. Jesse Goodman, an infectious disease specialist at Georgetown University Medical Center.

The Bright Side

This breakthrough comes after initial setbacks. The FDA rejected Moderna's first application in February because the company tested against standard flu shots instead of the high-dose vaccines typically recommended for adults 65 and older. But the strong results across all age groups suggest the mRNA vaccine would likely outperform even those stronger shots.

The FDA is expected to decide on approval by August 5. If approved, this would be the first mRNA-based flu vaccine anywhere in the world, using the same proven technology that powered successful COVID-19 vaccines.

Health experts emphasize the importance of keeping multiple vaccine technologies available. "With emerging pathogens and infections, it's difficult to predict which technology will rise to the top to make the best vaccine," said Dr. Peter Hotez of Baylor College of Medicine. Different technologies have proven crucial for different diseases, from Ebola to COVID-19.

For the 50 million Americans over 50 who get flu shots annually, better protection could mean fewer sick days, hospitalizations, and serious complications. That's progress worth celebrating.