The Food and Drug Administration has approved Moderna’s mFLUSIVA, the first mRNA based flu vaccine, for adults 50 and older. The vaccine relies on the same mRNA technology used in the company’s COVID-19 vaccine, marking a new direction in seasonal flu prevention for a population at higher risk of serious complications.
What mFLUSIVA is
mFLUSIVA, also known as mRNA-1010, is designed to protect older adults against seasonal influenza. Its approval followed a phase 3 clinical trial involving more than 40,000 participants across 11 countries. Results showed the vaccine outperformed the standard dose licensed flu vaccine in preventing lab confirmed flu like illness.
Why the technology is different
Most traditional flu vaccines are egg based and can take up to six months to manufacture, a timeline that sometimes leads to a mismatch between the vaccine formula and the strains actually circulating that season. mRNA vaccines can be developed and produced on a faster timeline, allowing manufacturers to adjust more quickly as flu strains shift.
mRNA vaccines can be redesigned more rapidly to keep pace with changing virus strains, potentially easing a longstanding challenge in flu prevention.
What the trial found
In adults ages 50 to 64, mFLUSIVA showed relative efficacy about 27% higher than the standard flu vaccine. The vaccine also received accelerated approval for people 65 and older, based on data showing a strong immune response compared with traditional options.
The vaccine as a meaningful addition to the tools available for flu prevention, particularly for older adults, who face a greater chance of complications from the virus.
The bigger public health picture
The Centers for Disease Control and Prevention estimated roughly 45,000 flu related fatalities in the United States during the 2024-2025 flu season, with vaccination efforts credited with preventing about 12,000 of those. If mFLUSIVA proves more effective than existing vaccines in real world use, it could contribute to lowering flu related mortality in the years ahead.
Side effects to know
As with any vaccine, mFLUSIVA carries the possibility of side effects. Those reported in clinical trials included headache, fatigue, joint pain, muscle pain, nausea, vomiting, fever and chills. Most were mild, though there is a small chance of a severe allergic reaction. Adults 50 and older are encouraged to talk with their health care provider about which flu vaccine best fits their health history.
Not a replacement, but another option
Experts stress that mFLUSIVA is meant to expand choices rather than replace existing flu vaccines. Trinh said the new option gives patients and providers more flexibility when protecting populations at higher risk from influenza.
Cutler agreed the vaccine shows promise but said more real world data is needed before it can be considered clearly superior to established options. He added that the most important step heading into flu season is getting vaccinated at all, whether with the new mRNA vaccine or a traditional one.
Looking ahead
Moderna‘s mFLUSIVA is expected to become available in the United States for the 2026-2027 respiratory virus season. For older adults who face a higher chance of complications from influenza, the vaccine offers an additional layer of protection built on technology that has already reshaped vaccine development in recent years.
