Pandemic influenza remains a significant global health threat, as signalled by the circulation and cross-species transmission of avian influenza A(H5N1) viruses from the clade 2.3.4.4b, including among dairy cattle in the USA since 2024. Although most of the reported human infections from the USA so far have been mild, the virus can change its profile rapidly. To reduce mortality and morbidity from influenza in humans, vaccines remain the most important intervention.
As part of ongoing work related to pandemic prevention and preparedness, WHO held a consultation on public health risk mitigation through A(H5N1) vaccines in September, 2024, which reviewed licensed H5 vaccines using publicly available and informally gathered information. As of September, 2024, there are at least 20 H5 influenza vaccines licensed by regulatory bodies in the Americas, Asia, Australia, and Europe. Most of these vaccines use inactivated influenza virus platforms and are produced from chicken eggs. Additionally, most are adjuvanted with squalene-based adjuvants or aluminium-based. All vaccines follow a two-dose schedule, with ten vaccines additionally indicated for children as young as six months and adults ages 65 years and older. So far, only one country (Finland) has implemented an A(H5) vaccination programme for at-risk groups.