The World Health Organization (WHO) has released its recommendations for the composition of influenza vaccines for the 2026-2027 northern hemisphere season, following a four-day consultation with global experts. The updated formula is designed to target the influenza strains expected to circulate later this year, offering optimal protection against severe illness.
The announcement comes as health officials note that influenza viruses are constantly evolving, requiring regular updates to vaccine formulations. This year’s recommendation follows the emergence of a new variant of the A(H3N2) virus in August 2025. Classified as a “subclade K” strain, this variant spread rapidly across the globe, contributing to an earlier start to the flu season in many countries and higher-than-usual levels of activity.
According to WHO surveillance data, influenza A viruses were predominant over the past season, with the new A(H3N2) variant accounting for the majority of cases reported across regions. Other variants of A(H3N2) and A(H1N1) were also detected, while influenza B viruses remained at low levels. Notably, no cases of the B/Yamagata lineage have been recorded since March 2020, confirming its continued absence from circulation.
For the upcoming season, WHO recommends that egg-based vaccines contain strains similar to A/Missouri/11/2025 (H1N1), A/Darwin/1454/2025 (H3N2), and B/Tokyo/EIS13-175/2025 (B/Victoria lineage). For cell culture-based, recombinant, or nucleic acid-based vaccines, the recommendations include strains similar to A/Missouri/11/2025, A/Darwin/1415/2025, and B/Pennsylvania/14/2025.
“Season after season, constantly evolving influenza viruses circulate globally, showing us how connected our world is, shared risks require shared action. Thanks to the Global Influenza Surveillance and Response System, next season’s vaccines have been updated to counter the latest strains, in turn better protecting communities.” said Dr Tedros Adhanom Ghebreyesus, WHO Director-General.
The consultation also reviewed zoonotic influenza viruses, including avian flu strains that have caused human infections. Since September 2025, 25 human cases of zoonotic influenza were reported from six countries, though no human-to-human transmission was documented. Experts recommended the development of a new candidate vaccine virus for an A(H9N2) strain as a precaution against potential pandemic threats.
Seasonal influenza remains a significant global health burden, with an estimated one billion cases annually and up to 650,000 respiratory deaths. National regulatory agencies and pharmaceutical companies will now use WHO’s recommendations to develop and license vaccines for the upcoming season.
Source: WHO
