There’s a new type of flu shot available this year, and you may be hearing about it for the first time. It’s called mFLUSIVA, and it uses the same kind of mRNA technology that many people got to know during the COVID-19 pandemic. If you’re wondering whether it’s right for you, here are clear answers to the most common questions.
What is the new mRNA Flu Vaccine?
mFLUSIVA is a new flu vaccine made by Moderna. The U.S. Food and Drug Administration (FDA) approved it for adults ages 50 and older. It’s the first mRNA-based flu shot to be approved in the United States.
Instead of using flu virus grown in eggs (the way most flu shots are made), mFLUSIVA uses a piece of genetic material called mRNA. It’s given as a single shot in the arm and protects against three flu strains: two influenza A strains and one influenza B strain chosen for the season.
How does the mRNA Flu Vaccine work? (can use photo here)
Think of mRNA as a set of instructions. The shot delivers these instructions inside a tiny fat bubble that helps them get into your cells. Once inside, your cells read the instructions and make a harmless piece of the flu virus, a surface protein called hemagglutinin.
Your immune system spots this protein, recognizes it as a stranger, and builds antibodies against it. If you’re later exposed to the real flu virus, your body already knows how to fight it. The mRNA doesn’t change your DNA, and it breaks down in your body after doing its job.
mRNA Flu Vaccine vs. Traditional Flu Vaccines
The biggest difference is how it’s made and how well it worked in testing.
- How it’s made: Traditional flu shots are mostly grown in eggs, which takes months. mRNA vaccines are made in the lab without eggs, so they can be updated faster to match the flu strains going around. There’s also no risk of “egg-based” changes that can make a vaccine match the virus less well. mFLUSIVA contains no egg protein, antibiotics, or preservatives.
- How well it works: In a large study of more than 40,000 adults ages 50 and up, people who got the mRNA vaccine had about 27% fewer confirmed flu cases than people who got a standard flu shot. In that study, about 2% of mRNA vaccine recipients got the flu, compared with about 2.8% of those who got the standard shot.
- Side effects: The trade-off is that the mRNA shot caused more temporary side effects. Sore arm, tiredness, headache, and muscle aches were more common than with a standard flu shot. Injection-site pain was reported about twice as often. Most of these were mild to moderate and went away on their own.
Is it better than the high-dose flu shot older adults often get?
Not clearly proven yet. In lab tests measuring antibodies, mFLUSIVA produced a stronger immune response than both standard-dose and high-dose flu shots. But we don’t yet have head-to-head proof that it prevents more actual flu illness than the high-dose shots made for older adults. Moderna will be running another study to answer this question.
Eligibility and Flu Vaccine Options: Who can get mFLUSIVA?
The FDA approved mFLUSIVA for adults 50 years of age and older. It is given as one 0.38 mL shot in the muscle. The approval for people 65 and older was based partly on antibody (immune response) data rather than direct flu-prevention data in that exact age group.
Q: Who should not get it, or should talk to a doctor first?
- People under 50: it isn’t approved for younger adults or children.
- People who are immunocompromised or taking medicines that suppress the immune system were not included in the main study, so it’s worth a conversation with your doctor.
- Anyone with a history of a severe allergic reaction to a previous dose or an ingredient in the vaccine.
If you’re not eligible for mFLUSIVA, remember that traditional flu shots remain a proven, effective choice, and getting any flu vaccine is far better than getting none.
Choosing between an mRNA Flu Shot and Traditional Flu Vaccines
There’s no single right answer for everyone. Here are some points to weigh with your doctor or pharmacist:
- You want the option with the strongest data showing fewer flu cases: mFLUSIVA reduced confirmed flu by about 27% compared with a standard shot in adults 50 and older.
- You want the most established, familiar option: Traditional flu shots have decades of use and cause fewer temporary side effects.
- You’re 65 or older: Both the mRNA vaccine and the high-dose or adjuvanted “enhanced” shots are reasonable. We don’t yet have proof that one prevents more flu illness than the other in this age group.
- You tend to have strong reactions to shots: Know that the mRNA vaccine is more likely to cause a sore arm, tiredness, or aches for a day or two.
The most important thing is to get vaccinated with one of the recommended options.
When is the best time to get the flu shot?
For most adults, the ideal time is October, before flu starts spreading widely in the community. This timing helps your protection stay strong through the peak of flu season which extends through April or later.
A few extra tips:
- Avoid July and August if you can, especially if you’re 65 or older, because protection can fade over the long season. The exception is if you’re worried you might not be able to get vaccinated later due to travel.
- Later is still worth it. If you miss the early window, getting vaccinated in November, December, or even later still helps, as long as flu is still going around.
- You generally only need one dose for the season.
The bottom line: mFLUSIVA is a promising new choice for adults 50 and older, but it’s one of several good options. Talk with your doctor or pharmacist about which flu vaccine fits you best, and aim to get it before flu season picks up.
Angela Jiang, MD; September 2026
Have Questions About the mFLUSIVA Vaccine?
If you have questions about the new mRNA mFLUSIVA vaccine or whether it may be appropriate for you, our Bay Area concierge medicine team can provide personalized guidance based on your health history and individual needs. We can help you understand how mFLUSIVA works, discuss potential benefits and considerations, and make informed decisions about your seasonal flu prevention. Contact us today at (650) 851-4747 or Contact us to schedule a consultation and take a proactive approach to protecting your health.
