Phase III Trial of mRNA Vaccine Against H5N1 Bird Flu Starts in UK and US

A phase III trial of an mRNA vaccine against the H5N1 bird flu strain has started in the UK and the US, @NewScientist reported. The mRNA-1018 vaccine, which has already completed phase I and II trials with no safety concerns identified, will involve 3000 volunteers in the UK and 1000 in the US.

The trial prioritizes people aged over 65 and those who work with poultry, as these groups face higher risks from the virus.

Since H5N1 bird flu is not spreading among people, the phase III trial will measure the strength of the immune response in volunteers rather than direct effectiveness. “A flu pandemic is the most likely future pandemic. And it’s really critical that we ensure we’re properly prepared,” said Richard Pebody at the UK Health Security Agency, as quoted by @NewScientist.

Results from earlier trials indicate the vaccine evokes a strong immune response, according to Hiwot Hiruy at Moderna. The trial is funded by the Coalition for Epidemic Preparedness Innovations (CEPI), which is backed by more than 30 countries and other organizations. This funding came after the US government cut support for mRNA vaccines.

“We cannot predict the timing or the severity of the next pandemic. However, with continued circulation of influenza viruses in animal populations, and the potential for virus adaptation, preparedness remains essential,” Hiruy stated. The UK has stockpiled 5 million doses of conventional vaccines against H5N1 bird flu, produced using chicken eggs.

These existing vaccines differ from the mRNA approach, which allows for rapid scaling and easy modifications if the virus evolves. Pebody noted that mRNA vaccines offer major advantages for pandemic preparation due to their flexibility in production.

A study in France found that vaccinating ducks dramatically reduced H5N1 outbreaks on farms, highlighting potential benefits for animal vaccination strategies.

Countries like the UK and US may consider rolling out H5N1 vaccines for farm animals, particularly poultry, building on such approaches used elsewhere. 4b has spread globally in wild birds since evolving around a decade ago. This strain has reached the Antarctic and has been circulating in dairy cattle in the US.

Many wild mammals have been infected by wild birds, and it has often spread to poultry farms. There have been more than 100 human cases of H5N1 bird flu since 2024. Despite these infections, there is no evidence of the virus spreading from person to person.

As long as H5N1 continues circulating, the risk of adaptation persists, underscoring the need for ongoing preparedness efforts.