Moderna’s mRNA flu vaccine receives first FDA approval, with 27% greater efficacy than conventional vaccine

Moderna’s mRNA-based seasonal flu vaccine, mFLUSIVA, was officially approved by the U.S. Food and Drug Administration on Aug. 5, 2026, local time, for adults age 50 and older. This marks the first time mRNA technology, which gained attention as a key public health tool during the COVID-19 pandemic, has been commercialized as a conventional seasonal flu vaccine. Moderna plans to supply mFLUSIVA to major pharmacies and health care institutions across the United States for the 2026-2027 flu season.

mFLUSIVA’s efficacy was confirmed in a large phase 3 clinical trial involving approximately 40,800 adults age 50 and older in 11 countries. Compared with participants who received a standard-dose flu vaccine, those who received mFLUSIVA had a 26.6%, or approximately 27%, lower risk of developing influenza-like illness. Temporary adverse effects, including injection-site pain, fatigue and headache, were reported somewhat more frequently than with the conventional vaccine, but no new or serious safety concerns were identified.

■ Structural limitations of conventional flu vaccines provide the backdrop

Traditional flu vaccines are produced using fertilized eggs or cell cultures, and the process takes approximately 6 months from selecting the virus strains to be included to completing production. As a result, a “mismatch” between the vaccine and the variant viruses circulating in practice has occurred repeatedly. By contrast, once the genetic antigen information is available, mRNA vaccines can be produced in 2 to 3 months, or as little as several weeks, making them better suited to incorporating the latest variants shortly before flu season begins.

The vulnerability of older adults to flu was another important factor behind the approval. In the United States, people age 65 and older account for less than 20% of the total population but represent 70% to 85% of flu-related deaths and 50% to 70% of hospitalizations each year. During the 2024-2025 season alone, approximately 45,000 flu-related deaths were recorded in the United States.

■ Unusual reversal occurred during FDA review

The approval process was not entirely smooth. The FDA initially refused to accept the application for review because the control group of adults age 65 and older had received a standard vaccine rather than a high-dose vaccine. After infectious disease experts strongly objected, warning that the decision could hinder innovation, the FDA reversed its decision within a week and resumed the review. Ultimately, the vaccine received full approval for adults age 50 to 64 and an Accelerated Approval for adults age 65 and older, contingent on completion of confirmatory trials. To obtain full approval for adults age 65 and older, Moderna must conduct additional trials over the next two flu seasons to demonstrate real-world efficacy.

Dr. Jeanne Marazzo, chief executive officer of the Infectious Diseases Society of America (IDSA), said, “This approval is a historic event both scientifically and from a public health perspective. The success of mRNA technology against flu opens the door to rapidly developing safe, targeted vaccines for a broader range of diseases.”

■ Relevance to South Korea’s aging society and the coming era of combination vaccines

South Korean researchers also contributed to the vaccine’s development. Lee Ji-won, a professor at Korea University College of Medicine, participated as a co-corresponding author on research showing that mFLUSIVA induces antibody responses against a broader range of flu variants than conventional vaccines. The study was published in the international journal Nature Immunology in June 2026.

South Korea is entering a super-aged society faster than any other country, making the prevention of respiratory infectious diseases among older adults a national priority. Industry experts believe that if an mRNA flu vaccine is introduced in South Korea, it could be used as a public health tool to reduce flu-related mortality and hospitalization rates among older adults during the winter. Regulatory authorities in Europe, Canada and Australia are also reviewing mFLUSIVA for approval.

The flexibility of mRNA technology is also drawing attention from a pandemic preparedness perspective. Even if a new pandemic-causing variant, such as avian flu, emerges, large-scale vaccine production could be possible within just a few weeks. Moderna is also accelerating commercialization of a combination vaccine that would prevent COVID-19 and flu at the same time, raising the possibility that the respiratory vaccine market itself could be reshaped.