Moderna starts Phase 3 H5N1 trial

Bird flu is an influenza virus that mostly spreads in birds, but H5N1 has also infected mammals and a small number of people. Moderna said on April 21 that the first volunteers have now been dosed in a Phase 3 trial of its mRNA-based H5 vaccine candidate, mRNA-1018. (accessnewswire.com) An mRNA vaccine works like a temporary set of instructions: it tells the body to make a harmless piece of a virus so the immune system can practice. Moderna’s late-stage study is designed to test whether mRNA-1018 safely triggers that immune response in healthy adults. (clinicaltrials.gov) (accessnewswire.com) The Phase 3 trial plans to enroll about 4,000 adults age 18 and older in the United States and United Kingdom. ClinicalTrials.gov lists the study start date as March 23, 2026, and estimates primary completion on January 28, 2027. (clinicaltrials.gov) Moderna said most clinical sites are in the U.K., with additional sites in the U.S., and outside reporting has said the U.K. network includes 26 sites. The company said the study is observer-blind, randomized and placebo-controlled. (accessnewswire.com) (msn.com) The financing behind the trial was lined up before dosing began. In December 2025, the Coalition for Epidemic Preparedness Innovations said it would invest up to $54.3 million to help move mRNA-1018 toward licensure. (cepi.net) That support came as H5N1 remained a pandemic planning concern rather than a broad human outbreak. Moderna said the current risk to the general human population remains low, but the virus continues to evolve and spread in birds and other animal hosts. (accessnewswire.com) The Global Virus Network reinforced that message on April 27, backing vaccine progress and calling for continued surveillance, biosecurity and preparedness. Its statement cited Moderna’s Phase 3 launch as a concrete sign that H5N1 vaccine work is moving beyond early testing. (eurekalert.org) Moderna also tied this program to its broader influenza platform. The company said future regulatory filings for mRNA-1018 would be supported by positive Phase 3 data from its seasonal flu vaccine candidate, mRNA-1010, which has been accepted for review in the U.S., European Union, Canada and Australia. (accessnewswire.com) For now, the key change is simple: H5N1 vaccine planning has moved into a 4,000-person Phase 3 test with volunteers already dosed. The next markers are immune-response and safety data as the trial runs through 2027. (clinicaltrials.gov) (accessnewswire.com)