UK and US Launch Human mRNA Bird Flu Vaccine Trials to Combat Pandemic Threat

A major clinical trial testing an mRNA vaccine against the H5N1 bird flu strain has begun in the United Kingdom and the United States, marking a significant step in pandemic preparedness efforts.

The vaccine, named mRNA-1018 and developed by Moderna, uses the same messenger RNA technology employed in the company’s Covid-19 vaccines. It is designed to instruct the body to produce specific viral proteins from the H5N1 strain, thereby training the immune system to recognize and respond to the virus if exposure occurs.

The phase 3 trial will involve approximately 4,000 participants across both countries. In the UK, 3,000 individuals are set to receive the vaccine at 26 sites spanning England and Scotland, with half of these participants aged over 65. The remaining 1,000 volunteers will be enrolled in the United States.

Participants will receive two doses of the vaccine administered three weeks apart, and the study is scheduled to run for seven months. The trial is backed by the National Institute for Health and Care Research (NIHR) and sponsored by Moderna.

Recruitment efforts are particularly targeting poultry farmers and individuals with close contact with birds, as these groups are considered at higher risk of exposure to the A(H5N1) strain. The virus has been spreading globally among bird populations and has recently infected other animal species, including mink, marine mammals, and dairy cows in the US, leading to a number of human cases among farm workers.

Although the threat of sustained human-to-human transmission of H5N1 remains low, experts emphasize that the potential for such transmission must be treated as a real possibility. Dr Rebecca Clark, the trial’s national co-ordinating investigator based at Layton Medical Centre in Blackpool, stated that while the virus does not yet move easily between humans, it is “evolving and spreading across animal species,” necessitating proactive measures.

Dr Hiwot Hiruy, senior director of clinical development at Moderna, noted that early trials of the vaccine found it to be “generally well tolerated, with most of the side-effects being mild to moderate, and there were no safety concerns.”

As of the latest reports, there have been 116 confirmed human cases of H5N1 infection worldwide since 2024, almost all linked to close contact with infected animals. The ongoing trial represents a key component of global efforts to prepare for a potential pandemic scenario should the virus acquire the ability to spread efficiently among people.