The first vaccine against influenza developed with messenger RNA technology has already arrived at pharmacies in the United States. It is mFlusiva, from the biotechnology company Moderna, now available at CVS pharmacies nationwide, while Walgreens is expected to receive its shipments at any moment.
The Food and Drug Administration (FDA) approved mFlusiva on August 6 for individuals aged 50 and older, paving the way for the vaccine to be ready before the start of flu season.
Who can get vaccinated with mFlusiva?
The FDA authorization sets clear limits: mFlusiva is intended exclusively for adults aged 50 and older.
The agency granted traditional authorization for the group aged 50 to 64 years and accelerated authorization for individuals aged 65 years and older, conditional on the conduct of an additional clinical trial in that age group.
Those who do not meet the age requirement can opt for any of the other flu vaccines approved for their age group.
How does it work and how does it differ from traditional vaccines?
Unlike conventional flu vaccines—which use inactivated versions of the virus, typically grown in eggs—mFlusiva introduces a small fragment of genetic code that trains the immune system to recognize and combat the virus.
"It’s like a temporary instruction for your immune system to alert your body’s natural defenses to recognize the flu," explained Emlah Tubuo, an independent pharmacist from Ohio, to NBC News.
The mRNA breaks down once its function is fulfilled and does not remain in the body. Protection takes about two weeks to develop after vaccination.
A significant advantage over traditional vaccines is their production speed: while conventional formulas require about six months to manufacture, mFlusiva can be produced in two to three months.
Dr. William Schaffner, an infectious disease specialist at the Vanderbilt University Medical Center, noted that this shorter timeframe "allows them to wait longer before deciding which strains to target, giving them a better idea of which ones are likely to be circulating."
Efficacy and safety
A Phase 3 clinical trial, published in May in the New England Journal of Medicine, evaluated over 40,000 adults aged 50 and older across 11 countries, including the United States.
The results showed that mFlusiva was approximately 27% more effective than a standard dose vaccine in preventing laboratory-confirmed illness.
FDA reviewers did not identify any serious safety issues. Side effects—pain at the injection site, fatigue, and headaches—were more common than in the standard vaccine group, but remained at mild to moderate levels.
Will the insurance cover the mFlusiva vaccine?
According to a report by NBC News, mFlusiva is arriving at pharmacies without a formal recommendation from the Centers for Disease Control and Prevention (CDC) or its advisory committee on vaccines, a step that usually precedes insurers covering vaccines at no cost.
A spokesperson for AHIP, an association of health insurers, indicated that they expect most private insurers to cover the vaccine.
For her part, Dorit Reiss, a vaccine policy expert at the University of California School of Law, stated that Medicare is required to fully cover the cost of seasonal flu vaccines that are approved by the FDA. However, she noted that it is unclear if this will happen this season, as the federal program has not yet received the aforementioned recommendation from the CDC.
According to the Centers for Medicare and Medicaid Services, mFlusiva costs about $171 per dose without insurance.
Depending on the pharmacy, the cost could be $154, according to GoodRx, a free digital platform in the United States that allows users to compare prices of prescription medications.
mFlusiva does not protect against COVID-19
Brigid Groves, a pharmacist with the American Pharmacists Association, clarified that mFlusiva "only targets the flu and is different from Moderna's combined COVID-19 and flu vaccine."
The vaccine is trivalent: it targets two strains of influenza A and one strain of influenza B, but it does not provide protection against the coronavirus.
Moderna's combined flu-COVID vaccine was approved by the European Union last April, but it has not yet received authorization in the United States.
The regulatory path for mFlusiva was not straightforward: in February, the FDA initially refused to review Moderna's application, citing that the clinical trial did not use the appropriate comparator for those over 65 years old. The agency reversed its decision days later, and in June, the independent advisory panel on vaccines unanimously recommended its approval.
The Centers for Disease Control and Prevention (CDC) recommend getting vaccinated before the end of October. The 2025-2026 flu season had a particularly severe impact in the United States: preliminary estimates from the CDC indicate approximately 390,000 hospitalizations and 24,000 deaths associated with influenza during that season.
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