The U.S. Food and Drug Administration has approved MFLUSIVA, Moderna’s mRNA-based seasonal flu vaccine, for people aged 50 and older. The FDA approved it as the first mRNA influenza vaccine, and manufacturers expect to make it available in the United States during the 2026–2027 respiratory virus season.
Quick Answer
MFLUSIVA is a seasonal influenza vaccine that uses messenger RNA to help the immune system recognize three flu-virus strains. It is given as a single injection and is approved only for adults aged 50 and older.
The approval for adults aged 65 and older was granted through the FDA’s accelerated-approval pathway based on immune-response results. Additional research must confirm its clinical benefit in that age group.
MFLUSIVA: Key Facts
| Detail | Information |
| Vaccine name | MFLUSIVA |
| Developer | Moderna |
| Vaccine type | Trivalent mRNA influenza vaccine |
| Approved age | 50 years and older |
| Dose | One 0.38 mL injection |
| Administration | Intramuscular injection |
| Targeted strains | A/H1N1, A/H3N2 and B/Victoria |
| FDA approval | August 5, 2026 |
| Expected availability | 2026–2027 U.S. respiratory season |
The vaccine contains three mRNA sequences encoding hemagglutinin proteins from the flu strains represented in the vaccine.
What Is MFLUSIVA?
MFLUSIVA, previously known as mRNA-1010, is a trivalent vaccine designed to prevent influenza caused by the influenza A and B strains included in its seasonal formula.
“Trivalent” means that the vaccine targets three major flu-virus groups:
- Influenza A/H1N1
- Influenza A/H3N2
- Influenza B/Victoria
Health authorities may update the composition for future flu seasons after reviewing which influenza strains are likely to circulate most widely.
The FDA-approved 2026–2027 formula comes as a single 0.38 mL dose that healthcare providers inject into a muscle, usually in the upper arm.
How Does an mRNA Flu Vaccine Work?
Messenger RNA, or mRNA, carries temporary instructions that cells can use to produce a specific protein.
After MFLUSIVA is administered, the mRNA instructs cells to produce harmless versions of influenza hemagglutinin proteins. The immune system identifies those proteins as foreign and develops an immune response against them.
If the vaccinated person later encounters a matching influenza virus, the immune system may recognize it and respond more quickly.
Vaccine mRNA does not enter the cell nucleus, where DNA is stored, and does not change a person’s DNA. Cells break down the mRNA after using its instructions. MedlinePlus explains how mRNA vaccines work.
Is MFLUSIVA Different From Traditional Flu Vaccines?
MFLUSIVA and traditional flu vaccines have the same broad purpose: preparing the immune system to respond to seasonal influenza. The main difference is how the vaccine presents flu antigens to the immune system.
Traditional flu vaccines may use:
- Inactivated influenza viruses
- Viruses grown in eggs or cell cultures
- Laboratory-produced influenza proteins
- Weakened live viruses in nasal vaccines
MFLUSIVA instead delivers mRNA instructions that enable cells to temporarily produce selected influenza proteins.
Because the mRNA manufacturing process does not depend on growing vaccine viruses in eggs, it can also avoid egg-adaptive changes that can occur during some traditional production processes. The CDC provides an overview of the different types of flu vaccines.
What Did the MFLUSIVA Clinical Trial Find?
The main Phase 3 trial included nearly 40,700 adults aged 50 and older across 11 countries. Participants received either MFLUSIVA or a licensed standard-dose influenza vaccine.
MFLUSIVA demonstrated 26.6% relative vaccine efficacy against laboratory-confirmed influenza-like illness compared with the standard-dose vaccine used in the study.
This result does not mean that MFLUSIVA provides only 26.6% protection overall. It means that, during the trial, the risk of the study-defined influenza outcome was 26.6% lower in the MFLUSIVA group than in the group receiving the comparison flu vaccine.
For participants aged 65 and older, the FDA considered immune-response data comparing Moderna’s mRNA vaccine platform with a high-dose influenza vaccine.
The FDA granted approval for this older age group under the accelerated-approval pathway. The agency requires a confirmatory study to verify the vaccine’s clinical benefit in people aged 65 and older.
What Are the Possible Side Effects?
The most commonly reported reactions in clinical trials included:
- Pain at the injection site
- Fatigue
- Headache
- Muscle pain
- Joint pain
- Chills
- Underarm swelling or tenderness
- Nausea, vomiting or fever in some participants
In adults aged 50–64, injection-site pain was reported by 68.7% of participants, fatigue by 48.1% and headache by 41.9%.
Among participants aged 65 and older, injection-site pain was reported by 62.9%, fatigue by 42.1% and headache by 33.7%.
Most recorded reactions were mild or moderate and lasted for a median of approximately two days.
Who Should Not Receive MFLUSIVA?
According to the FDA prescribing information, people with a history of a severe allergic reaction, such as anaphylaxis, to MFLUSIVA or one of its ingredients should not receive the vaccine.
People should discuss the vaccine with a healthcare professional when they:
- Previously developed Guillain-Barré syndrome within six weeks of a flu vaccination
- Have a weakened immune system
- Take medicines that suppress the immune response
- Have previously fainted after injections
- Are pregnant, planning pregnancy or breastfeeding
An impaired immune system may produce a weaker response to the vaccine, and no vaccine protects every recipient. The FDA’s complete MFLUSIVA prescribing information contains the full warnings and safety information.
Can MFLUSIVA Cause Influenza?
MFLUSIVA does not contain a live influenza virus. It supplies temporary mRNA instructions for selected viral proteins, so the vaccine itself cannot infect a person with influenza.
Temporary symptoms such as fatigue, muscle pain, headache or fever can occur after vaccination as the immune system responds. These reactions are not the same as contracting influenza.
When Will MFLUSIVA Become Available?
Moderna says it expects MFLUSIVA to be available to eligible adults in the United States during the 2026–2027 respiratory virus season.
Approval does not necessarily mean the vaccine will immediately be available at every pharmacy or medical clinic. Distribution dates, insurance coverage and local availability may differ.
Update the article when pharmacies begin stocking the vaccine and when the CDC releases final seasonal recommendations that include MFLUSIVA.
Why Is This Approval Important?
The approval introduces a new vaccine technology into the seasonal influenza market.
The mRNA platform may allow manufacturers to update vaccine strains without using eggs to grow influenza viruses. However, the real-world performance of MFLUSIVA will require continued monitoring across future flu seasons.
The approval does not mean that existing influenza vaccines are ineffective or that every eligible adult should automatically choose MFLUSIVA. The most suitable vaccine may depend on age, medical history, availability and professional guidance.
For more health reporting, visit our Public Health news and explainers.
Frequently Asked Questions
Q1. Is MFLUSIVA the first mRNA flu vaccine?
Yes. Moderna describes MFLUSIVA as the first mRNA-based influenza vaccine approved by the FDA. The FDA licensed it for adults aged 50 and older in August 2026.
Q2. Is MFLUSIVA a COVID-19 vaccine?
No. It uses mRNA technology, but it protects against seasonal influenza strains rather than the virus that causes COVID-19.
Q3. Does the mRNA flu vaccine change DNA?
No. Vaccine mRNA does not enter the nucleus, which stores DNA, and cells break down the mRNA after using its instructions.
Q4. Can people under 50 receive MFLUSIVA?
The FDA currently approves MFLUSIVA only for people aged 50 and older. Its FDA labeling does not include younger adults or children.
Q5. Is it approved for people over 65?
Yes. For people aged 65 and older, it received accelerated approval based on immune-response findings. Continued approval may depend on a confirmatory clinical trial.
Q6. Is one dose required?
The FDA prescribing information lists a single 0.38 mL intramuscular dose for the 2026–2027 formula.
Final Takeaway
MFLUSIVA adds a new mRNA-based option to seasonal flu vaccination for adults aged 50 and older.
Clinical research found that it reduced laboratory-confirmed influenza-like illness relative to a standard-dose comparison vaccine, although it also produced more short-term reactions such as injection-site pain, fatigue and headache.
Its approval represents an important development in vaccine technology, but individual vaccination decisions should still be made using current public-health recommendations and advice from qualified healthcare professionals.
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Medical Disclaimer
This article is for general informational purposes only. It does not provide medical advice, diagnosis or treatment. Readers should consult a qualified healthcare professional regarding vaccination decisions, health conditions or possible side effects.
