Moderna Launches Phase III H5N1 mRNA Vaccine Trial

A phase III clinical trial for an mRNA vaccine against the H5N1 bird flu strain has begun in the United Kingdom and the United States, marking a key step in preparing for a potential influenza pandemic. The trial, led by pharmaceutical company Moderna, involves approximately 4,000 volunteers, with the majority recruited across 26 sites in England and Scotland, and the remainder in the U.S. First immunizations occurred this week at clinics including one in Southampton, targeting high-risk groups such as poultry workers and individuals over 65.

The vaccine, known as mRNA-1018, employs the same messenger RNA technology proven effective in COVID-19 shots. It works by instructing cells to produce proteins mimicking those of the H5N1 virus, training the immune system to recognize and fight the pathogen. Since the virus does not currently spread efficiently between humans, the trial focuses on safety and the strength of immune responses rather than direct efficacy against infection. Participants receive two doses three weeks apart, with early phase I and II studies showing the vaccine was well-tolerated, with mostly mild side effects and no major safety issues. Immune responses...