April 22, 2026

Launch of new human vaccine trial: mRNA vaccine candidate against H5N1 bird flu

A new vaccine trial is starting in the UK investigating an mRNA vaccine candidate against A(H5N1) bird flu, in humans.  This is a phase 3 trial and will involve around 4,000 adult volunteers aged 18 and over, 75% of whom will be recruited and vaccinated at UK sites (the rest being in the US).

H5N1 bird flu has been spreading globally in wild and farmed birds, including some cases in commercial poultry in the UK over the last couple of years.  It has also spread to some mammals including cattle in the US.  It does not easily spread to humans, and the rare human cases there have been have been linked to close contact with infected birds.  But as part of preparedness for potential future outbreaks and pandemics, scientists are investigating candidate vaccines for humans in case they are needed in future.

This trial will look at whether the vaccine can elicit an immune response in the human volunteers.  This trial is at launch stage, so no results yet.  The trial will prioritise over-65s and farmers who deal with poultry since they are most at risk from bird flu.

This briefing was brought to us by the NIHR and Moderna.  The study is supported by the NIHR and sponsored by Moderna, as part of its UK government strategic partnership, which is managed by the UKHSA, and the study is also supported by Moderna’s collaboration with CEPI (the Coalition for Epidemic Preparedness Innovations).

Journalists dialled in to this briefing to hear from the scientists who are running the trial and to answer their questions.

Speakers included:

Dr Rebecca Clark, Principal Investigator at Fylde Coast Clinical Research, and co-clinical lead at UK Vaccine Innovation Pathway

Dr Hiwot Hiruy, Senior Director, Clinical Development, Moderna

Dr Richard Pebody, Director of Epidemic and Emerging Infections, UKHSA

This Briefing was accompanied by an SMC Roundup of comments.