The U.S. Food and Drug Administration (FDA) has approved mFlusiva (mRNA-1010), Moderna's messenger RNA (mRNA)-based influenza vaccine, making it the first licensed influenza vaccine developed using mRNA technology in the United States.
The approval marks another expansion of mRNA technology beyond COVID-19 vaccines and introduces a new platform for seasonal influenza vaccination. It also marks the first time an influenza vaccine using mRNA technology has reached the U.S. market, extending a platform first widely used during the COVID-19 pandemic into seasonal influenza prevention. Moderna announced that it expects to make doses available at select retailers before the 2026-2027 influenza season.
The FDA granted traditional approval for adults aged 50 to 64 years and accelerated approval for adults aged 65 years and older, with the condition that Moderna conduct a post-marketing Phase 4 clinical study to confirm effectiveness in the older age group.
Moderna Chief Executive Officer Stéphane Bancel said the approval demonstrates the versatility of the company's mRNA platform and provides another option for older adults, who remain at higher risk of severe influenza.
The approval represents more than the launch of another seasonal influenza vaccine.
It marks the first regulatory authorization of an mRNA influenza vaccine and demonstrates that the platform can be successfully applied beyond COVID-19.
Scientists have long viewed influenza as a promising target for mRNA technology because influenza viruses change frequently, requiring vaccine formulations to be updated almost every year. A shorter manufacturing timeline could eventually provide manufacturers with greater flexibility when responding to evolving influenza strains or future influenza pandemics.
First FDA-approved mRNA influenza vaccine
40,805 participants enrolled in the pivotal Phase 3 trial
Clinical trial conducted across 11 countries
26.6% relative vaccine efficacy compared with a licensed standard-dose influenza vaccine
Adults aged 65 years and older accounted for approximately 57% of influenza-related hospitalizations during the 2024-2025 U.S. influenza season
Adults aged 65 years and older accounted for approximately 71% of influenza-related deaths during the 2024-2025 U.S. influenza season
Influenza causes seasonal outbreaks every year and can lead to complications such as pneumonia, worsening of chronic medical conditions, hospitalization, and death, particularly among older adults, young children, pregnant women, and people with weakened immune systems.
According to data cited by Moderna and the U.S. Centers for Disease Control and Prevention (CDC), adults aged 65 years and older accounted for approximately 57% of influenza-related hospitalizations and 71% of influenza-related deaths during the 2024-2025 influenza season.
Although seasonal influenza vaccines reduce the risk of illness and severe outcomes, vaccine effectiveness varies from year to year because influenza viruses constantly evolve.
Unlike conventional influenza vaccines that generally require influenza viruses to be grown in chicken eggs or cell cultures before vaccine production begins, mRNA vaccines use a different approach.
Instead of introducing viral proteins directly, an mRNA vaccine delivers genetic instructions enclosed within lipid nanoparticles. After vaccination, cells temporarily use these instructions to produce harmless influenza hemagglutinin (HA) proteins, which stimulate the immune system to generate protective antibodies and immune responses. The mRNA does not enter the cell nucleus or alter a person's DNA. It is naturally broken down after protein production.
Unlike egg-based influenza vaccines, mRNA vaccines do not require manufacturers to grow influenza viruses before production. Once the genetic sequence of the selected influenza strains is available, synthetic mRNA can be designed and manufactured before being packaged into lipid nanoparticles. Although annual strain selection remains necessary, this approach could shorten production timelines and provide greater flexibility if circulating influenza viruses change unexpectedly.
One of the biggest challenges in influenza vaccination is timing.
Each year, the World Health Organization (WHO) recommends which influenza virus strains should be be included in seasonal vaccines several months before the start of the influenza season. Manufacturers using traditional egg-based or cell-based production methods require this long lead time because producing millions of vaccine doses takes months.
As influenza viruses continue to mutate after strain selection, the viruses circulating during flu season may differ from those included in the vaccine, reducing vaccine effectiveness.
According to Moderna, production from strain selection to vaccine availability can take approximately two to three months, compared with around six months for conventional influenza vaccines. A shorter production timeline may allow manufacturers to update vaccine strains closer to the influenza season, potentially improving the match between vaccines and circulating viruses. However, annual global surveillance and strain selection will continue to remain essential because influenza viruses constantly evolve.
The FDA's decision was primarily supported by results from the randomized, observer-blind, active-controlled Phase 3 clinical trial (NCT06602024) involving 40,805 adults aged 50 years and older across 11 countries.
Participants received either a single dose of mFlusiva or a licensed standard-dose quadrivalent influenza vaccine. The study used an active comparator rather than a placebo because seasonal influenza vaccination is already recommended for older adults.
The trial evaluated both vaccine safety and relative vaccine efficacy, which measures how much better one vaccine performs compared with another rather than against no vaccination.
According to Moderna, mFlusiva demonstrated 26.6% relative vaccine efficacy compared with the licensed standard-dose comparator vaccine, meeting the study's predefined superiority criterion.
Among adults aged 65 years and older, relative vaccine efficacy reached 27.4%, although this age group received accelerated rather than traditional approval because additional confirmatory effectiveness data are still required.
| Parameter | Details |
|---|---|
| Trial | NCT06602024 |
| Design | Phase 3, randomized, observer-blind, active-controlled |
| Participants | 40,805 adults aged 50 years and older |
| Countries | 11 |
| Primary endpoint | RT-PCR-confirmed influenza-like illness |
| Relative vaccine efficacy | 26.6% versus a licensed standard-dose influenza vaccine |
| Approval pathway for adults aged ≥65 years | Accelerated approval supported by immunogenicity data and additional clinical evidence; a post-marketing Phase 4 confirmatory study is required |
| Safety | No new safety signals identified |
The reported 26.6% relative vaccine efficacy does not mean the vaccine prevents influenza in only 26.6% of people.
Instead, it means that participants who received mFlusiva experienced approximately 27% fewer laboratory-confirmed influenza illnesses than participants who received the licensed standard-dose comparator vaccine during the study.
This comparison is important because influenza vaccines are already widely recommended, making placebo-controlled trials less appropriate in many populations.
Beyond demonstrating superiority over a standard-dose influenza vaccine, the Phase 3 study provides the first large-scale evidence that an mRNA platform can be successfully adapted for seasonal influenza vaccination. If future post-marketing studies confirm these findings, the technology could influence how seasonal influenza vaccines are developed and manufactured.
The path to approval was not straightforward.
In February 2026, the FDA issued Moderna a Refusal-to-File (RTF) letter, stating that it would not review the company's Biologics License Application (BLA) in its current form. The decision drew attention because Refusal-to-File letters are uncommon for late-stage vaccine applications that have completed large Phase 3 clinical trials.
The FDA's initial concern centered on the choice of comparator vaccine rather than the safety or efficacy of mFlusiva itself.
According to documents released by Moderna, the FDA questioned the company's decision to compare mFlusiva with a licensed standard-dose influenza vaccine in adults aged 65 years and older instead of a high-dose or adjuvanted influenza vaccine, which are preferentially recommended for this age group in the United States.
Moderna responded that the trial design had been discussed with the FDA before participant enrollment and noted that several countries participating in the multinational study did not routinely use high-dose or adjuvanted influenza vaccines for older adults. Following further discussions, the FDA agreed to review the application.
The issue became one of the most closely watched regulatory developments involving an mRNA vaccine after COVID-19 because it raised questions about clinical trial design, comparator selection, and regulatory expectations for vaccines intended for older adults.
The FDA approved mFlusiva through two regulatory pathways based on age group.
Adults aged 50 to 64 years received traditional approval, supported by clinical efficacy data from the Phase 3 trial.
Adults aged 65 years and older received accelerated approval, supported primarily by immunogenicity data from a separate randomized clinical trial (NCT05827978) involving 2,992 participants, which compared mFlusiva with a licensed high-dose influenza vaccine.
Accelerated approval allows the FDA to approve certain products based on evidence that is reasonably likely to predict clinical benefit while requiring additional post-marketing studies to confirm their effectiveness.
Under this pathway, Moderna must complete a Phase 4 confirmatory study to verify the vaccine's clinical benefit in older adults.
Before the FDA reached its final decision, the Vaccines and Related Biological Products Advisory Committee (VRBPAC) reviewed the available evidence in June 2026.
Committee members unanimously concluded that the available data demonstrated that the vaccine's benefits outweighed its risks for adults aged 50 years and older.
Although VRBPAC recommendations are not legally binding, they often play an important role in FDA vaccine decision-making.
The Phase 3 clinical program found that mFlusiva had an acceptable safety profile, with no new safety signals identified.
The most commonly reported adverse reactions included:
Injection-site pain
Fatigue
Headache
Muscle pain (myalgia)
Fever
Most reactions were mild to moderate in severity and generally resolved within one to two days.
Researchers reported that local and systemic reactions occurred more frequently than with the licensed standard-dose comparator vaccine. However, the overall safety profile remained consistent with previous mFlusiva studies.
The FDA has nevertheless required additional post-marketing evaluation in adults aged 65 years and older to further assess clinical effectiveness following widespread use.
Influenza viruses continuously change through a process known as antigenic drift, in which small genetic changes accumulate over time. These changes can alter viral proteins enough to reduce how well existing immunity recognizes newly circulating strains.
For this reason, the World Health Organization reviews global influenza surveillance data each year and recommends which virus strains should be included in the next seasonal vaccine. Manufacturers then produce updated vaccines based on those recommendations before the influenza season begins.
Several influenza vaccine technologies are currently available, each using a different production approach.
| Feature | Egg-based | Cell-based | Recombinant | mFlusiva (mRNA) |
|---|---|---|---|---|
| Production platform | Virus grown in fertilized chicken eggs | Virus grown in mammalian cell culture | Recombinant hemagglutinin protein | Synthetic mRNA packaged in lipid nanoparticles |
| Manufacturing time | Approximately 6 months | Several months | Several months | Approximately 2 to 3 months, according to Moderna |
| Virus cultivation required | Yes | Yes | No | No |
| Potential for faster strain updates | Limited | Moderate | Moderate | Higher |
Although mRNA technology may shorten manufacturing timelines, its long-term performance across multiple influenza seasons will continue to be evaluated through post-marketing surveillance and future studies.
Moderna plans to make mFlusiva available ahead of the 2026-2027 influenza season.
The vaccine has also been accepted for regulatory review in the European Union, Canada, and Australia, with additional international submissions planned during 2026.
The required Phase 4 study will help determine whether mFlusiva provides sustained protection in adults aged 65 years and older compared with currently recommended high-dose influenza vaccines, while also confirming its long-term clinical effectiveness in this higher-risk population.
Researchers are also evaluating broader applications of mRNA technology, including combination vaccines targeting influenza and COVID-19, as well as vaccines against additional infectious diseases.
Myth: mRNA vaccines change a person's DNA.
Fact: Messenger RNA remains outside the cell nucleus and provides temporary genetic instructions that allow cells to produce influenza proteins, triggering an immune response. The mRNA is naturally broken down after protein production and does not alter human DNA.
The approval of mFlusiva expands the clinical use of mRNA technology beyond COVID-19 and respiratory syncytial virus (RSV), providing another example of how the platform can be adapted for seasonal infectious diseases.
While conventional influenza vaccines remain effective and continue to play an important role in preventing severe illness, hospitalization, and death, mRNA technology offers a different manufacturing approach that may provide greater flexibility when circulating influenza strains evolve or when rapid vaccine production is needed during a future influenza pandemic.
While mFlusiva represents the first FDA-approved mRNA influenza vaccine, its long-term role in seasonal influenza prevention will depend on real-world effectiveness across multiple influenza seasons and results from the required post-marketing study in adults aged 65 years and older.
U.S. Food and Drug Administration. Vaccines and Related Biological Products Advisory Committee (VRBPAC) June 18, 2026 Meeting Announcement: MFLUSIVA (Influenza Vaccine, mRNA).
https://www.fda.gov/advisory-committees/advisory-committee-calendar/vaccines-and-related-biological-products-advisory-committee-june-18-2026-meeting-announcement
Moderna. “IR Insights: Introducing mFLUSIVA – A Milestone for Moderna's Respiratory Portfolio.” August 5, 2026. Accessed August 6, 2026. https://www.modernatx.com/ir-insights-mflusiva
ClinicalTrials.gov. A Study to Evaluate the Efficacy, Safety, and Immunogenicity of mRNA-1010 Seasonal Influenza Vaccine in Adults 50 Years of Age and Older (NCT06602024).
https://clinicaltrials.gov/study/NCT06602024
ClinicalTrials.gov. A Study Evaluating the Safety and Immunogenicity of mRNA-1010 Compared With High-Dose Influenza Vaccine in Adults 65 Years of Age and Older (NCT05827978).
https://clinicaltrials.gov/study/NCT05827978
U.S. Food and Drug Administration. Accelerated Approval Program.
https://www.fda.gov/drugs/nda-and-bla-approvals/accelerated-approval-program
U.S. Centers for Disease Control and Prevention (CDC). How Flu Viruses Can Change: Drift and Shift.
https://www.cdc.gov/flu/about/viruses/change.htm
U.S. Food and Drug Administration. Influenza Vaccine Composition for the 2026-2027 U.S. Influenza Season.
https://www.fda.gov/vaccines-blood-biologics/vaccines/influenza-vaccine-composition-2026-2027-us-influenza-season
World Health Organization. Recommended Composition of Influenza Virus Vaccines for Use in the 2026-2027 Northern Hemisphere Influenza Season.
https://cdn.who.int/media/docs/default-source/vcm-northern-hemisphere-recommendation-2026-2027/a.-27-feb-2026-recommended-composition-of-influenza-virus-vaccines-for-use-in-the-2026-2027-nouthern-hemisphere-influenza-season---full-report.pdf