Tejal Somvanshi
The United States has its first influenza vaccine built on the same messenger RNA technology that powered COVID-19 shots. On 5 August 2026, the Food and Drug Administration approved mFlusiva, made by the Massachusetts-based company Moderna, for adults aged 50 and older. Moderna expects the shot to be available at select pharmacies this autumn, ahead of the flu season.
The approval rests on a study of more than 40,000 adults aged 50 and over who received either mFlusiva or a standard inactivated flu vaccine. During the 2024-25 respiratory virus season, those given the mRNA shot had about 27 per cent fewer cases of flu than those given the conventional vaccine, according to Moderna’s announcement.
Traditional flu vaccines are usually grown in chicken eggs and contain inactivated pieces of the virus to train the immune system. The mRNA version instead carries genetic instructions that teach cells to make a flu protein, prompting the body to build defences. That approach can be manufactured far faster. Because egg-based production must begin many months before a season, a mismatch between the predicted and actual circulating strain is hard to correct. An mRNA vaccine could in principle be updated in a couple of months, narrowing the gap between the shot and the virus that is actually spreading.
Research published in Nature Immunology in June 2026 found the mRNA vaccine produced a stronger and longer-lasting immune response than conventional flu shots. People who received it had markedly higher levels of flu antibodies one month after vaccination, and those levels persisted for six months, suggesting the protection lasts longer. Conventional vaccines are typically between 40 and 60 per cent effective at preventing infection in a given year.
Moderna’s trials showed the strongest benefit in older adults, especially those over 65, which is why the initial approval covers people 50 and older. The most common side effects were injection-site reactions such as pain and swelling, along with fatigue, headache, muscle or joint pain, nausea and fever.
Each year influenza kills thousands of Americans and hospitalises tens of thousands more. The approval marks the first time mRNA technology has been used for a seasonal flu vaccine in the United States, offering adults aged 50 and older a new option ahead of this year’s flu season.
