US approves first mRNA-based seasonal flu vaccine

The Food and Drug Administration (FDA) approved Moderna’s mFlusiva vaccine for adults aged 50 and older, making it the US’ first approved seasonal influenza vaccine based on messenger RNA technology.

The vaccine received traditional approval for adults between 50 and 64. and accelerated approval for those 65 and older, Moderna announced Wednesday.

The accelerated approval for the older age group was based on evidence that mFlusiva generated a strong immune response. Moderna is required to conduct an additional study to confirm its clinical benefits for those 65 and older, with continued approval potentially depending on the findings.

“Flu remains a significant public health challenge, and mFLUSIVA provides an important new option for America’s seniors,” said Moderna Chief Executive Officer Stephane Bancel.

The approval was supported by a late-stage clinical trial involving more than 40,000 adults aged 50 and older.

The trial found that mFlusiva was 26.6% more effective at preventing laboratory-confirmed influenza-like illness than a licensed standard-dose flu vaccine.

A separate study involving about 3,000 adults aged 65 and older found that mFlusiva produced stronger antibody responses against the tested influenza strains than a high-dose flu vaccine.

Reactions such as pain at the injection site, fatigue, headaches and muscle pain were more common among mFlusiva recipients than among those who received comparison vaccines, according to the FDA’s review. Most reactions were mild or moderate and lasted about two days.

Serious adverse events and deaths were reported at similar rates in the vaccine and comparison groups, while no cases of myocarditis or pericarditis were identified within 42 days of vaccination, said the review.

Unlike most conventional flu vaccines, which are produced using eggs, mFlusiva uses mRNA to instruct the body to produce influenza antigens and trigger an immune response.

The technology could allow vaccine manufacturers to update flu shots more quickly to better match circulating strains.

Moderna said it expects mFlusiva to become available to eligible adults in the US during the 2026-2027 respiratory virus season. Applications are also under review in the EU, Canada and Australia.