The World Health Organization (WHO) has announced its recommendations for the viral composition of influenza vaccines for the 2026 influenza season in the southern hemisphere. The announcement followed a four-day consultation involving experts reviewing surveillance data and other relevant information to guide vaccine formulation. Regular updates to influenza vaccine composition are essential due to the constantly evolving nature of the viruses, ensuring continued effectiveness and protection of public health worldwide.
WHO convenes these consultations twice a year, once for each hemisphere, bringing together advisory experts from WHO Collaborating Centres and Essential Regulatory Laboratories. These experts review data from the WHO Global Influenza Surveillance and Response System (GISRS) and its collaborators to inform their recommendations, which serve as the basis for national and regional regulatory authorities, pharmaceutical manufacturers, and other stakeholders to develop, produce, and license influenza vaccines.
For the 2026 southern hemisphere influenza season, WHO recommends that trivalent egg-based vaccines contain an A/Missouri/11/2025 (H1N1)pdm09-like virus, an A/Singapore/GP20238/2024 (H3N2)-like virus, and a B/Austria/1359417/2021 (B/Victoria lineage)-like virus. For cell culture-, recombinant protein-, or nucleic acid-based vaccines, the recommended strains are an A/Missouri/11/2025 (H1N1)pdm09-like virus, an A/Sydney/1359/2024 (H3N2)-like virus, and a B/Austria/1359417/2021 (B/Victoria lineage)-like virus.
The advisory committee continues to maintain its position that a B/Yamagata lineage antigen is no longer warranted, consistent with the last four recommendations since September 2023. Quadrivalent vaccines, where the transition from trivalent is incomplete, may still include a fourth component, the B/Yamagata lineage virus (B/Phuket/3073/2013-like virus), but no updated recommendations will be issued for this component.
WHO has also provided updated guidance for developing new candidate vaccine viruses for zoonotic influenza, aiming to strengthen global pandemic preparedness and response.
