FDA Approves mFlusiva, the First mRNA-Based Influenza Vaccine

The FDA approved Moderna’s mRNA (mRNA)-based seasonal influenza vaccine, mFlusiva (mRNA-1010), for use in adults aged 50 years and older. With this action, the vaccine has become the first influenza vaccine built on mRNA technology to reach the US market.¹

Clinical Evidence Supporting the Approval

The indication’s approval was based on efficacy data from the phase 3 FLUENT (NCT06602024)², a randomized, observer-blind, active-controlled, case-driven study that randomly assigned adults 50 years of age or older to receive the trivalent mRNA vaccine (37.5 μg, which includes 12.5 μg of each strain) or a licensed standard-dose comparator. FLUENT’s primary efficacy end point was relative vaccine efficacy against reverse-transcriptase–polymerase chain reaction (RT-PCR)–confirmed, protocol-defined influenza-like illness caused either by influenza A or B, from at least 14 days after vaccination through the end of the influenza season. Hypothesis testing was conducted hierarchically to assess noninferiority.^2,3

A total of 40,703 adults were enrolled in the trial, about half of whom received the mRNA vaccine, and the remainder received a licensed standard-dose comparator vaccine. According to data published in the New England Journal of Medicine, mFlusiva met all primary end points—including noninferiority and superiority over the standard-dose vaccine—and demonstrated approximately 26.6% relative efficacy against protocol-defined influenza-like illness caused by influenza A or B. Solicited adverse events (AEs) were more common with the mRNA vaccine than with standard-dose comparators, including injection-site pain (65.8%), fatigue (45.1%), and headache (37.8%); however, the FLUENT investigators reported that most AEs considered mild to moderate and transient.³

Prior to Approval, mFlusiva Faced Scrutiny

In February 2026, the FDA’s Center for Biologics Evaluation and Research (CBER) issued a refusal-to-file (RTF) letter for the original mFlusiva application, declining to review it at all. The letter, which was signed by then-CBER director Vinay Prasad, MD, MPH, stated that the sole reason for the refusal was Moderna’s use of a licensed standard-dose influenza vaccine as the comparator in its pivotal trial, which the agency argued did not represent the “best-available standard of care” for older adults, despite neither federal regulation nor FDA guidance explicitly requiring such a comparator. The agency did not raise any concerns regarding the vaccine’s safety or efficacy.⁴

About 1 week after the RTF letter, following public disclosure of the decision and Moderna’s objections, the FDA reversed its stance. The company proposed a revised, age-stratified regulatory strategy—full approval for adults aged 50 to 64 years and accelerated approval for adults 65 years and older alongside a postmarketing study using a high-dose comparator in the older cohort—and the agency accepted the amended application with a Prescription Drug User Fee Act date of August 5, 2026.⁵

In June 2026, the FDA’s Vaccines and Related Biological Products Advisory Committee unanimously voted to recommend mFlusiva for adults aged 50 years and older, which was the panel’s first review of a new vaccine application since May 2023.⁶

“Flu remains a significant public health challenge, and mFlusiva provides an important new option for America’s seniors,” Stéphane Bancel, Moderna’s chief executive, said in an article from The New York Times. “This approval also reflects the ongoing potential of our mRNA platform to help address important public health challenges through continued scientific innovation.”¹

Political Backdrop and What Comes Next

The approval arrives amid continued public friction over mRNA vaccines from US Department of Health and Human Services Secretary Robert F. Kennedy Jr, and it follows a period in which the CDC’s Advisory Committee on Immunization Practices (ACIP)—the body that determines how a newly approved vaccine is used and whether it is covered by insurance—was itself contending with a legal dispute over its composition and authority following a federal court ruling.⁶ How quickly ACIP issues use recommendations, and whether insurers cover the vaccine as a result, will shape how much of the 2026-2027 flu season mFlusiva is able to reach.

For pharmacists, the approval introduces a fourth mRNA product to routine immunization conversations alongside Moderna’s COVID-19 and respiratory syncytial virus vaccines, plus a novel platform question in the crowded field of preferred flu vaccines for older adults. Pharmacists should be ready to explain that mFlusiva’s approval is split by age: adults aged 50 to 64 years received a standard approval, whereas those 65 years and older received an accelerated approval that still requires a postmarketing confirmatory trial against a high-dose comparator; therefore, outcome data in the group at highest risk for flu complications is not yet complete.

Although they were generally mild to moderate and transient, patients may also ask about AEs, since injection-site pain, fatigue, and headache were more common with mFlusiva in the FLUENT trial. Coverage and insurance reimbursement may also lag the FDA approval given the ongoing ACIP dispute, so pharmacists should be prepared for questions about cost and availability as the 2026 to 2027 season approaches, and should discourage patients from delaying vaccination altogether while waiting for the new option to become more widely available.

REFERENCES

1. Jewett C. F.D.A. Approves Moderna’s mRNA Flu Vaccine. The New York Times. August 5, 2026. Accessed August 6, 2026. https://www.nytimes.com/2026/08/05/health/mrna-flu-vaccine-moderna.html?smid=nytcore-ios-share

2. A Study of mRNA-1010 Compared With a Licensed Influenza Vaccine in Adults ≥50 Years of Age. ClinicalTrials.gov identifier: NCT06602024. Updated September 10, 2025. Accessed August 6, 2026. https://clinicaltrials.gov/study/NCT06602024

3. Leroux-Roels I, Huang G, Ferguson M, et al. Efficacy and safety of an mRNA seasonal influenza vaccine in adults. N Engl J Med. 2026;394(18):1803-1813. doi:10.1056/NEJMoa2516491

4. Ferruggia K. FDA declines to review Moderna's mRNA-1010 flu vaccine application, citing comparator concerns. Pharmacy Times. February 11, 2026. Accessed August 6, 2026. https://www.pharmacytimes.com/view/fda-declines-to-review-moderna-s-mrna-1010-flu-vaccine-application-citing-comparator-concerns

5. Ferruggia K, Yang T. After refusal-to-file, FDA reconsiders Moderna's mRNA flu vaccine with higher bar for older adults. Pharmacy Times. February 18, 2026. Accessed August 6, 2026. https://www.pharmacytimes.com/view/after-refusal-to-file-fda-reconsiders-moderna-s-mrna-flu-vaccine-with-higher-bar-for-seniors

6. Antrim A. FDA panel unanimously backs Moderna's breakthrough mRNA flu vaccine amid political turbulence. Pharmacy Times. June 19, 2026. Accessed August 6, 2026. https://www.pharmacytimes.com/view/fda-panel-unanimously-backs-moderna-s-breakthrough-mrna-flu-vaccine-amid-political-turbulence