The US Food and Drug Administration has approved Moderna’s mFlusiva, making it the first mRNA-based seasonal influenza vaccine cleared for public use. The vaccine is approved for adults aged 50 years and older and is expected to become available in the United States during the 2026–2027 respiratory virus season.
The decision represents an important expansion of messenger RNA technology beyond COVID-19 and respiratory syncytial virus vaccines. It also introduces another preventive option for older adults, who face a higher risk of serious complications from seasonal influenza.
According to Reuters, the FDA granted different forms of approval based on age:
- Traditional approval for adults aged 50 to 64 years
- Accelerated approval for adults aged 65 years and older
- A requirement for Moderna to conduct further research confirming clinical benefits in the older population
Accelerated approval allows the FDA to clear a medical product using evidence that is considered reasonably likely to predict clinical benefit. Continued approval may depend on the successful completion of a post-marketing confirmatory study.
What is mFlusiva?
mFlusiva, previously known as mRNA-1010, is a trivalent seasonal influenza vaccine developed by Moderna. It uses messenger RNA carried inside lipid nanoparticles to instruct cells to produce influenza antigens that stimulate an immune response.
According to FDA briefing documents, the vaccine targets three influenza components:
- Influenza A/H1N1
- Influenza A/H3N2
- Influenza B/Victoria lineage
The vaccine contains 12.5 micrograms of mRNA for each component, for a total mRNA dose of 37.5 micrograms. It is administered as a single 0.375-millilitre intramuscular injection supplied in a prefilled syringe.
Unlike many conventional flu vaccines, mFlusiva does not depend on growing influenza viruses in eggs. Its mRNA platform instead provides genetic instructions for producing selected viral antigens.
This production method may offer greater flexibility when updating vaccine composition. However, its real-world manufacturing and public-health advantages will need to be evaluated over multiple influenza seasons.
Phase 3 trial involved more than 40,000 adults
The FDA’s decision was supported by results from a Phase 3 clinical study involving 40,805 adults aged 50 years and older across 301 clinical sites in 11 countries.
Participants were randomly assigned to receive either mFlusiva or a licensed standard-dose influenza vaccine. The study was conducted during the 2024–2025 Northern Hemisphere influenza season.
Among participants included in the primary efficacy analysis:
- 411 of 20,179 mFlusiva recipients developed laboratory-confirmed, protocol-defined influenza-like illness.
- 557 of 20,124 standard-dose vaccine recipients developed the same outcome.
- mFlusiva achieved 26.6% relative vaccine efficacy compared with the standard-dose vaccine.
- The reported 95% confidence interval was 16.7% to 35.4%.
The 26.6% figure does not mean that the vaccine prevented 26.6% of all influenza infections. It represents the additional reduction in influenza risk compared with an already approved standard-dose flu vaccine—not compared with a placebo or no vaccination.
Results were broadly consistent across the principal age groups. Relative efficacy was estimated at:
- 26.1% among adults aged 50 to 64
- 27.4% among adults aged 65 and older
- 28.0% among adults aged 65 to 74
For participants aged 75 and older, the point estimate was 25.3%, but the confidence interval crossed zero. The FDA said this result was less certain because fewer participants and influenza cases were available in that subgroup.
Evidence for adults aged 65 and older
For adults aged 65 years and older, Moderna also compared the vaccine’s immune response with Sanofi’s Fluzone High-Dose vaccine.
A separate Phase 3 study included approximately 3,000 older adults. The mRNA vaccine produced stronger antibody responses against the influenza strains assessed in the trial.
However, stronger antibody measurements do not automatically establish superior real-world protection against influenza illness, hospitalization or death. For that reason, the FDA used the accelerated approval pathway for people aged 65 and older.
Moderna is expected to conduct a large post-marketing study to verify mFlusiva’s clinical benefit in this population. The proposed research could include approximately 800,000 adults aged 65 and older across two influenza seasons.
What did researchers find about safety?
FDA reviewers reported that mFlusiva caused more short-term reactions than the comparison vaccines. Most reactions were described as mild to moderate and generally resolved within approximately two days.
Frequently reported reactions included:
- Pain at the injection site
- Fatigue
- Headache
- Muscle pain
- Joint pain
- Chills
- Fever
- Swelling or tenderness near the armpit
In the main Phase 3 study, 67.5% of participants in the mFlusiva safety subset reported a local reaction, compared with 32.1% of people receiving a standard-dose vaccine.
Systemic reactions were reported by 58.0% of mFlusiva recipients and 32.4% of comparator recipients. Grade 3 systemic reactions—severe enough to interfere with normal daily activity—occurred in 5.5% and 0.9%, respectively.
Across the pooled safety analysis, serious adverse events occurred in 3.1% of mFlusiva recipients and 2.9% of comparator-vaccine recipients. Deaths from all causes were reported at approximately 0.3% in both groups during the follow-up period.
The FDA concluded that overall rates of serious adverse events, deaths and adverse events of special interest were balanced between the groups. Post-marketing safety monitoring will continue following the vaccine’s commercial introduction.
Why is the approval significant?
The approval gives Moderna its first seasonal flu vaccine and broadens the commercial use of its mRNA platform.
Potential features of the platform include:
- A production process that does not require growing influenza viruses in eggs
- The ability to design vaccine antigens using influenza genetic sequences
- Potentially faster adjustment when recommended influenza strains change
- A common technology platform that could support future respiratory-virus vaccines
These potential advantages should not be interpreted as proof that every mRNA vaccine will be faster to produce or more effective than every conventional vaccine. Performance will depend on vaccine design, circulating strains, manufacturing capacity and supporting clinical evidence.
The approval may also support Moderna’s longer-term work on a combined influenza and COVID-19 vaccine. That combination product remains separate from mFlusiva and would require its own regulatory review before entering the US market.
Innovation supports growth of the global vaccines market
The approval of the first mRNA flu vaccine reflects broader innovation across the global vaccine industry. Manufacturers are increasingly investing in new vaccine platforms designed to address seasonal infections, emerging pathogens and previously unmet healthcare needs.
According to Medi-Tech Insights, the global vaccines market is projected to grow at a CAGR of 7% during the 2026–2031 forecast period. Key factors supporting this growth include:
- Rising prevalence of infectious diseases
- Increasing investment in vaccine research and development
- Growing awareness of the benefits of immunization
- Introduction of innovative vaccines targeting unmet healthcare needs
- Continued government support for vaccination programs
The development of mRNA-based influenza vaccines could contribute to this market expansion by encouraging further investment in advanced vaccine technologies. However, future adoption will depend on regulatory decisions, clinical evidence, vaccine recommendations, pricing, reimbursement and public acceptance.
When will mFlusiva be available?
Moderna said it expects mFlusiva to be available to eligible US adults during the 2026–2027 respiratory virus season.
Actual availability may vary by healthcare provider, pharmacy, insurer and region. Public-health recommendations will also influence how the vaccine is used, particularly among people aged 65 and older, for whom enhanced or high-dose influenza vaccines have historically been preferred.
Consumers should consult a qualified healthcare professional about the most appropriate influenza vaccine based on their:
- Age
- Medical history
- Allergy history
- Previous vaccine reactions
- Current health conditions
- Local public-health guidance
Key facts about the first mRNA flu vaccine
- Vaccine name: mFlusiva
- Development name: mRNA-1010
- Manufacturer: Moderna
- Vaccine type: Trivalent mRNA influenza vaccine
- Approved population: Adults aged 50 years and older
- Traditional approval: Ages 50–64
- Accelerated approval: Ages 65 and older
- Dose: 37.5 micrograms of total mRNA
- Administration: Single 0.375-mL intramuscular injection
- Main Phase 3 study size: 40,805 participants
- Relative efficacy versus a standard-dose vaccine: 26.6%
- Expected US availability: 2026–2027 respiratory virus season
Frequently asked questions
What is the first approved mRNA flu vaccine?
mFlusiva, developed by Moderna, is the first approved seasonal influenza vaccine that uses mRNA technology. The FDA has approved it for adults aged 50 years and older.
Who can receive mFlusiva?
The vaccine is approved for people aged 50 and older in the United States. Adults aged 50 to 64 received coverage under the traditional approval pathway, while people aged 65 and older were covered through accelerated approval.
Is mFlusiva more effective than a standard flu vaccine?
In a Phase 3 study, mFlusiva demonstrated 26.6% relative vaccine efficacy compared with a licensed standard-dose influenza vaccine. This reflects its additional benefit over the comparison vaccine and should not be interpreted as absolute effectiveness against influenza.
Is the vaccine approved for adults younger than 50?
No. The current FDA approval covers adults aged 50 years and older. Use in younger people would require additional clinical evidence and regulatory authorization.
What are the common side effects?
Common reactions include injection-site pain, fatigue, headache, muscle pain, joint pain, chills, fever and swelling or tenderness near the armpit. Most reported reactions were mild to moderate and resolved within a short period.
Does mFlusiva provide complete protection against influenza?
No vaccine provides complete protection. Effectiveness can vary by age, immune status, circulating influenza strains and how closely the vaccine composition matches those strains.
What happens next?
The launch of mFlusiva will provide the first opportunity to assess an approved mRNA seasonal flu vaccine in routine clinical practice.
Key developments to watch include:
- Results from Moderna’s confirmatory study in adults aged 65 and older
- Real-world effectiveness during different influenza seasons
- Safety findings from broader post-marketing surveillance
- Vaccine uptake and insurance coverage
- Future regulatory decisions outside the United States
- Progress on combined influenza and COVID-19 vaccines
The FDA approval marks a notable scientific and regulatory milestone, but longer-term evidence will determine how mFlusiva compares with established standard-dose, high-dose and adjuvanted influenza vaccines in everyday use.
Jeff Berman is a healthcare and medical technology journalist with over 7 years of experience covering the global medtech, biotechnology, pharmaceutical, and healthcare sectors. As a contributor to Just MedTech, he specializes in industry news, market trends, regulatory developments, mergers and acquisitions, and emerging innovations shaping the future of healthcare worldwide. Contact: jeff.b@justmedtech.com.