FDA Approves First-Ever mRNA Flu Vaccine, Marking a Historic Win for Moderna

The US Food and Drug Administration has approved Moderna’s mFlusiva for adults aged 50 and older, making it the first mRNA-based influenza vaccine cleared in the United States.

The decision gives older adults a new seasonal flu option and extends messenger RNA technology beyond Covid-19 vaccines. It also ends an unusual seven-month review in which the FDA initially refused to consider Moderna’s application before accepting a revised regulatory plan.

Moderna expects mFlusiva to be available for the 2026–27 US flu season, although supply, insurance coverage and pharmacy access may vary.

What is mFlusiva and who can receive it?

mFlusiva, previously known as mRNA-1010, is a trivalent vaccine targeting influenza A/H1N1, A/H3N2 and the B/Victoria lineage.

Instead of growing influenza viruses in eggs, the vaccine delivers temporary genetic instructions that help the immune system recognize selected flu proteins. The mRNA does not enter the cell nucleus and is broken down after delivering those instructions.

The FDA approval covers adults aged 50 and older. It does not currently include younger adults, teenagers or children.

• Ages 50 to 64: The vaccine received traditional approval based on clinical efficacy and safety results.
• Ages 65 and older: It received accelerated approval based partly on antibody-response data, with Moderna required to complete another study confirming its benefit.

Accelerated approval does not mean the vaccine avoided a full safety review. It allows approval using evidence considered likely to predict clinical benefit while additional research continues.

How effective was Moderna’s flu vaccine?

Moderna’s main trial involved more than 40,000 adults aged 50 and older. Participants received either mFlusiva or an existing standard-dose flu vaccine.

mFlusiva showed 26.6% relative vaccine efficacy compared with the standard-dose vaccines. That does not mean it prevented only 26.6% of infections. It means qualifying flu cases were 26.6% lower in the mFlusiva group than in the comparison group.

The vaccine also produced a 47.9% relative reduction in influenza cases requiring hospitalization, emergency-room care or urgent treatment.

Its real-world performance may vary each season depending on circulating strains, vaccine matching and the health of the person receiving it.

Why did the FDA initially refuse the application?

The FDA’s concern centered on the vaccine used for comparison in adults aged 65 and older. Moderna’s main trial compared mFlusiva with standard-dose flu vaccines rather than directly tracking flu cases against Fluzone High-Dose, which is commonly recommended for seniors.

Moderna later submitted immune-response data showing that mFlusiva generated stronger antibody responses against matched strains than Fluzone High-Dose. However, that study measured antibodies rather than actual infection rates.

After discussions with the FDA, Moderna agreed to seek traditional approval for adults aged 50 to 64, accelerated approval for adults 65 and older and conduct a confirmatory study involving as many as 800,000 people over two flu seasons.

The FDA then resumed the review, and an advisory committee voted unanimously in June to recommend the vaccine for adults aged 50 and older.

What is known about safety?

Common reactions included injection-site pain, fatigue, headache, muscle pain, joint pain, chills, nausea and fever. Most reported reactions were mild or moderate and lasted about two days.

Serious adverse events were generally balanced between mFlusiva and the comparison vaccines during the trials. Patients should still tell a healthcare professional about previous severe allergic reactions, immune conditions or a history of Guillain-Barré syndrome after a flu shot.

Official product and safety information is available through Moderna’s mFlusiva information page.

How is it different from traditional flu vaccines?

Many conventional flu vaccines are produced using viruses grown in chicken eggs, a process that can take about six months. Manufacturers must therefore select strains well before flu season begins.

Moderna’s mRNA platform may allow vaccines to be designed and produced in roughly two to three months. A shorter production window could help manufacturers match the vaccine more closely to circulating strains, although faster manufacturing does not guarantee better protection every year.

The wider role of seasonal vaccination and global immunization efforts is explored in this overview of vaccine access and immunization progress.

When will mFlusiva be available?

Moderna says it plans to supply mFlusiva for the 2026–27 flu season. However, many seasonal vaccine contracts are agreed earlier in the year, which may limit first-season availability.

Broader commercial adoption may not arrive until the 2027–28 season, when pharmacies, health systems and insurers have more time to add the vaccine to their purchasing plans.

FDA approval also does not automatically guarantee insurance coverage. CDC recommendations and individual plan rules may influence reimbursement and where the vaccine is offered.

Why the approval matters for Moderna

mFlusiva gives Moderna another product beyond its Covid-19 business and strengthens its respiratory vaccine pipeline. The company is also developing a combined Covid-flu shot, which previously faced delays after regulators requested more influenza data.

Approval of mFlusiva supports the flu component of that programme, but the combination vaccine will still require separate evidence and regulatory clearance.

The development also adds context to Moderna’s revenue outlook and vaccine pipeline as the company seeks sustainable growth beyond pandemic-era Covid vaccine sales.

For adults aged 50 and older, mFlusiva is a new option rather than an automatic replacement for existing high-dose, adjuvanted, recombinant or standard-dose flu vaccines. The most appropriate choice will depend on age, health history, availability and advice from a qualified healthcare professional.