Moderna starts Phase 3

Bird flu is an influenza virus that usually spreads in birds, not people. Moderna has now started a Phase 3 study of an mRNA H5 vaccine candidate, mRNA-1018, in adults in the U.S. and U.K. (investors.modernatx.com, pharmafocusamerica.com) Messenger RNA, or mRNA, works like a set of genetic instructions that tells the body to make a harmless piece of a virus so the immune system can practice against it. Moderna said first participants have already been dosed in the late-stage trial. (emjreviews.com, pharmafocusamerica.com) The Phase 3 study is designed to enroll about 4,000 adults age 18 and older. Moderna said researchers will measure safety and immune response, including whether the vaccine triggers antibodies against H5 influenza. (pharmafocusamerica.com, medicaleconomics.com) This is late-stage testing for a virus health agencies have been tracking across birds, poultry flocks, and U.S. dairy cattle. The Centers for Disease Control and Prevention says H5 bird flu has caused sporadic human infections, mostly after direct exposure to infected poultry or dairy cows. (cdc.gov, cdc.gov) The Centers for Disease Control and Prevention says the current risk to the general public remains low. It also says people with close or prolonged exposure to infected animals face higher risk, and that the virus is being monitored through flu surveillance systems. (cdc.gov, cdc.gov) The cattle piece changed the picture in 2024. The Centers for Disease Control and Prevention says the multistate outbreak in dairy cows was first reported on March 25, 2024, the first time these bird flu viruses had been found in cows. (cdc.gov) Moderna had been building this program before the new trial began. A ClinicalTrials.gov record for its Phase 1/2 study says the earlier study was meant to generate enough safety and immune-response data to support selection of one vaccine candidate for a large Phase 3 trial. (clinicaltrials.gov) Funding for the late-stage study came from the Coalition for Epidemic Preparedness Innovations, or CEPI. CEPI said in December 2025 that it would invest up to $54.3 million to help advance mRNA-1018 toward licensure and included supply commitments for low- and middle-income countries in the agreement. (cepi.net, biopharmadive.com) Moderna said any future regulatory filing for mRNA-1018 could also draw support from data in its separate seasonal flu vaccine program, mRNA-1010, which the company says is already under review in the European Union, Canada, and Australia. In February 2026, Moderna also said the U.S. Food and Drug Administration had issued a refusal-to-file letter for that seasonal flu application in the United States. (newswire.com, investors.modernatx.com) What happens next is straightforward: Moderna has to show in thousands of adults that mRNA-1018 is safe and produces the immune response regulators want to see. The trial starts with a virus that still poses low public risk today, but one health agencies and vaccine makers are treating as a pandemic threat worth preparing for now. (pharmafocusamerica.com, cdc.gov)