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The Food and Drug Administration approved Mflusiva, a Moderna flu shot built on messenger RNA (mRNA) technology, Aug. 5 for adults 50 and older. It gives people in that age group a new kind of flu shot for the 2026-27 season.
Flu activity is still low nationwide but rising, the Centers for Disease Control and Prevention reported Oct. 2. Since protection takes about two weeks to build after a shot, health authorities advise getting vaccinated by the end of October.
The approval works differently by age. For adults 50 to 64, it rests on a large trial that counted flu cases. For those 65 and older, the FDA used accelerated approval, a faster pathway based on early evidence such as antibody levels. Moderna must confirm the benefit in a new study.
How does the new mRNA flu shot for people 50 and older work?
Most of the flu vaccine supply is produced using chicken eggs. Mflusiva skips that process. It delivers mRNA, a set of genetic instructions for hemagglutinin, a protein on the flu virus’s outer surface.
The shot covers this season’s three selected strains: two influenza A strains (H1N1 and H3N2) and one influenza B strain. Tiny fat particles carry the instructions into cells. The cells then make the protein, which trains the immune system to recognize the real virus.
How well does the mRNA flu shot work?
In a trial of about 40,800 adults 50 and older, Mflusiva lowered the risk of lab-confirmed flu illness by 26.6% compared with a standard-dose shot, FDA reviewers found. About 2% of recipients got sick, versus 2.8% in the comparison group.
What are the side effects of the mRNA flu shot?
The trade-off is more short-term side effects. Within a week, about 76% of Mflusiva recipients reported reactions, compared with 47% in the standard-dose group. The most common were pain at the injection site, fatigue, headache, muscle aches and chills. Most were mild to moderate and short-lived.
As a condition of approval, Moderna must keep tracking the vaccine’s safety, including deaths and certain heart and nerve conditions, after FDA reviewers flagged questions they couldn’t fully resolve from trial data.
Where can you get the new flu shot if you’re 50 or older?
Mflusiva is given as a single injection into the muscle. Pharmacies and doctors’ offices may offer it, but many haven’t stocked it yet because it’s so new. Calling ahead or checking Moderna’s online vaccine locator can save a trip.
Does Medicare cover the new flu shot?
If you have Medicare, Part B covers one flu shot each season at no cost when your provider accepts assignment meaning it takes Medicare’s approved amount as full payment. Since Mflusiva is new, ask your pharmacy whether it can bill Medicare for it.
Who should check with a doctor before getting the mRNA flu shot?
Talk to your provider before booking if you plan to get other vaccines at the same visit. FDA reviewers noted there’s no data yet on giving Mflusiva alongside COVID-19, respiratory syncytial virus (RSV) or pneumonia vaccines.
The same goes for people with weakened immune systems, very frail older adults, and anyone who developed Guillain-Barre syndrome, a rare nerve disorder, within six weeks of a past flu shot. If Mflusiva isn’t available nearby, other flu vaccines are, including enhanced shots designed for adults 65 and older.