The FDA has recently approved Moderna’s mRNA flu vaccine. The vaccine, known as mFLUSIVA (mRNA-1010), is designed to protect adults ages 50 years and older against seasonal flu. It is the first mRNA-based flu vaccine, using similar technology as the mRNA COVID-19 vaccine.
The FDA approved the vaccine based on the results of a phase 3 clinical trial involving more than 40,000 adults ages 50 and older across 11 countries. Around half of the participants received mFLUSIVA, and the other half received a standard-dose licensed flu vaccine.
The researchers concluded that mFLUSIVA was superior to the standard-dose licensed flu vaccine in preventing flu-like illness confirmed by real-time polymerase chain reaction (RT-PCR) lab tests.
The vaccine was also granted accelerated approval for use in adults ages 65 years and older. This was following a clinical trial involving over 2,900 adults in the United States. The study evaluated how well the immune system responded to mFLUSIVA compared with a high dose inactivated flu shot.
Moderna expects that mFLUSIVA will be available in the United States for the 2026 to 2027 respiratory virus season.
There were an estimated 45,000 flu-related deaths in the United States in the 2024 to 2025 flu season, according to the most recent data from the Centers for Disease Control and Prevention (CDC). They noted that vaccination was estimated to have prevented around 12,000 deaths.
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As the research found that mFLUSIVA has the potential to be more effective at reducing the risk of flu than other vaccines, it could help further prevent flu-related deaths.
Medical News Todayspoke with Dung Trinh, MD, internist, of MemorialCare Medical Group and Chief Medical Officer of Healthy Brain Clinic in Irvine, CA, about the importance of this latest vaccine.
Trinh, who was not involved in the trials, viewed the FDA approval of mFLUSIVA as “an important addition to our influenza prevention toolkit, particularly because adults over 50 begin to experience a progressively higher risk of serious complications from influenza.”
He added: “This is also a significant scientific milestone because it is the first mRNA-based seasonal influenza vaccine approved in the United States, showing that mRNA technology can be applied beyond COVID-19.”
David Cutler, MD, board certified family medicine physician at Providence Saint John’s Health Center in Santa Monica, CA, also spoke with MNTabout the new vaccine.
“My overall view is cautiously favorable. The FDA approval of Moderna’s mFLUSIVA (mRNA-1010) is scientifically interesting and potentially important, but I would not interpret it as proof that the mRNA vaccine is necessarily the best flu vaccine for every person over 50,” said Cutler, who was not involved in the trials.
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He also explained that the FDA’s approval has important distinctions, with “traditional/full approval” for people aged 50 to 64, and “accelerated approval, with a requirement for additional post-approval evidence confirming clinical effectiveness” for adults ages 65 and over.
“That distinction matters,” continued Cutler, “because people ≥65 are the group in which we most want to know whether the vaccine actually prevents hospitalization, pneumonia, and death, rather than simply producing higher antibody levels.”
Flu viruses are constantly changing. This means that, by the time manufacturing is finished and the vaccines are ready to be administered, the virus may have altered, and the shot might not be as effective as it would have been at the beginning of the manufacturing process.
It can take at least 6 months to manufacture a traditional egg-based flu vaccine, according to the FDA.
However, the mRNA vaccine can be produced more quickly, which means it may be more likely to keep up with the rapid changes of the virus.
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Cutler described “a potentially important technological advantage” of the mRNA vaccine, explaining that they “can theoretically be redesigned and manufactured more rapidly when influenza strains change. That could become increasingly valuable for influenza, where vaccine-virus mismatch is a perennial problem.”
Based on study findings, the mRNA flu vaccine has the potential to be more effective than traditional flu vaccines.
“For adults ages 50 to 64, the approval was based on a randomized phase 3 trial involving more than 40,000 participants, in which mFLUSIVA demonstrated approximately 27% greater relative vaccine efficacy against confirmed influenza compared with a standard-dose flu vaccine, while the clinical program identified no new safety concerns,” explained Trinh.
“I think the larger significance of mFLUSIVA may ultimately be beyond influenza itself,” added Cutler.
“If mRNA technology proves capable of producing more effective, rapidly updated influenza vaccines, it could substantially change how we respond to seasonal influenza and potentially to future influenza pandemics,” he said.
Like any vaccine, the mRNA flu vaccine may lead to side effects.
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According to Moderna, general side effects that were reported in the clinical trials included:
There were also reactions at the injection site. In rare cases, a severe allergic reaction or anaphylaxis could occur.
Before getting the mRNA flu vaccine, Moderna recommends informing a healthcare professional if:
Moderna advises against getting mFLUSIVA if the person has had a severe reaction to any of its ingredients.
As with any vaccine, a healthcare professional can advise on its safety and whether they recommend it based on individual circumstances.
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For individuals ages 50 years and over, they can speak with their doctor about the type of flu vaccine they recommend and when they should receive it.
The mRNA flu vaccine is not designed to immediately replace traditional flu vaccines.
“I think the appropriate way to view this is not as a replacement for every existing flu vaccine, but as another evidence-based option that could ultimately give physicians and patients more choices in protecting people at higher risk from influenza,” Trinh explained.
Cutler said, “mFLUSIVA is an exciting new option, and its trial results are encouraging. But because its FDA approval in ≥65 is accelerated and confirmatory clinical-outcome data are still required, I would want to see another season or two of real-world evidence before declaring it superior to the established enhanced vaccines.”
He added: “For the 2026 to 2027 season, the most important decision is still to get an appropriate flu vaccine rather than waiting for the ‘perfect’ vaccine. The new mRNA option gives physicians and patients another potentially very useful tool.”
