Bird flu vaccine trial against potential pandemic strain begins

The UK has initiated the first phase of a vaccine trial aimed at combating a possible bird flu pandemic. This new vaccine is designed to combat the H5N1 strain, which has caused significant outbreaks in bird populations globally and has also been observed in some mammalian species. While the risk to humans remains relatively low, the UK Health Protection Agency notes that nearly all human infections are connected to direct exposure to infected animals.

Utilizing mRNA technology, a method already proven effective in Covid-19 vaccinations, the vaccine can be developed rapidly and in large quantities. Scientists highlight that this approach allows for swift production and adaptation, crucial in the event of a pandemic. The trial prioritizes individuals in high-risk categories, including poultry workers and those aged 65 and above.

“It was quite easy and it could be something that ultimately proves incredibly important,” said Clare Howard, a Hampshire-based poultry farmer who participated in the trial at a Southampton clinic.

The trial will involve 4,000 participants, with three-quarters recruited from 26 locations across England and Scotland, and the remaining in the United States. Dr. Rebecca Clark, the trial’s national co-ordinating investigator, noted that the strain is “evolving and spreading across animal species.” She added, “Although it does not yet move easily between humans, we have to treat human-to-human transmission as a real possibility. This trial is our proactive attempt to shield against that possibility, and any future pandemic that could emerge from it.”

Since 2024, 116 human cases of H5N1 have been documented globally, with almost all linked to close contact with infected animals. The study will evaluate the vaccine’s safety and its ability to trigger a robust immune response. If successful, it could be authorized for use during a potential outbreak.

Professor Lucy Chappell, chief scientific adviser at the Department of Health and Social Care, called the trial “bolstering our pandemic resilience.” If needed, the vaccine will be manufactured at Moderna’s new Harwell facility in Oxfordshire, which currently produces Covid vaccines for the UK. The plant can generate 100 million doses annually, with capacity to scale up to 250 million in a pandemic scenario.

The conventional approach to flu vaccine production relies on culturing the virus in chicken eggs. However, this method can be problematic with virulent avian strains that may destroy the eggs during manufacturing. During the Covid-19 crisis, mRNA vaccines demonstrated high efficacy in preventing severe illness, and could be produced and modified rapidly as strains evolved.

Flu pandemics are an inevitable occurrence, even if the timing of the next global outbreak is uncertain. The flu virus constantly evolves, necessitating new vaccinations each year. A pandemic arises when a strain changes significantly enough that humans lack natural immunity. The 2009 swine flu pandemic, though relatively mild, was a stark reminder of the virus’s potential.

In contrast, the Spanish flu pandemic following World War I claimed over 50 million lives globally. While the potential for H5N1 to trigger the next pandemic remains uncertain, there have been other experimental vaccines targeting this strain. A similar trial in Oxford in 2006 tested an early version, but the jab, although safe, was not highly effective.

Recent reports indicate that a U.S.-circulating variant of the virus has resulted in less severe symptoms, with eye inflammation being the primary manifestation. In August 2025, the U.S. government reduced funding for mRNA vaccines by $500 million after health secretary Robert F Kennedy Jr, a vaccine sceptic, argued that “mRNA technology poses more risks than benefits” for respiratory viruses.

CEPI, the Coalition for Epidemic Preparedness Innovations, has stepped in to provide £40 million in funding for this trial, ensuring fast and affordable vaccine access for low- and middle-income countries in any future pandemic. CEPI emphasized that this investment aims to counter vaccine nationalism, which left millions unprotected during the early stages of the Covid-19 crisis.