On Dec. 18, 2024, a team of researchers reported results from preclinical testing of mRNA-based vaccines against Highly pathogenic avian influenza (HPAI). The vaccines, which are based on A(H5) clade 2.3.4.4b viruses, conferred protection in ferrets subsequently challenged with A(H5N1). Serum from vaccinated ferrets also neutralized an HPAI A(H5N1) isolate collected from an infected human in 2024.

Two doses of mRNA vaccination elicited robust neutralizing antibody titers against a 2022 avian isolate and a 2024 human isolate. Further, mRNA vaccination conferred protection from lethal challenge, whereas all unvaccinated ferrets succumbed to infection. It also reduced viral titers in the upper and lower respiratory tracts of infected ferrets. These results underscore the effectiveness of mRNA vaccines against HPAI A(H5N1), showcasing their potential as a vaccine platform for future influenza pandemics.

A(H5N1) continues to spread throughout domestic poultry and cattle, with occasional transmission to humans. Although human-to-human transmission has not yet been reported, steps need to be taken to prepare should that occur.