Influenza Vaccine Composition Recommendations for 2026 2027 Season

The World Health Organization (WHO) today announced recommendations for the viral composition of influenza (or 'flu') vaccines for the 2026-2027 northern hemisphere influenza season. The announcement was made following a 4-day consultation examining global influenza surveillance data.

Influenza vaccine composition must be regularly updated because influenza viruses are constantly changing. WHO’s recommendations are used by national vaccine regulatory agencies and pharmaceutical companies around the world to develop, produce, and license influenza vaccines for the following influenza season. This ensures that vaccines are closely matched to the viruses expected to circulate, offering the best possible protection against severe illness and death.

Held twice a year, once for each of the northern and southern hemispheres, these consultations gather experts from WHO’s Collaborating Centres and Essential Regulatory Laboratories of the WHO Global Influenza Surveillance and Response System (GISRS) to review and analyze data generated by GISRS and its partners.

'Season after season, constantly evolving influenza viruses circulate globally, showing us how connected our world is. Shared risks require shared action,' said Dr. Tedros Adhanom Ghebreyesus, WHO Director-General. 'WHO’s recommendations for influenza vaccine composition rest on the diligent, year-round work of the Global Influenza Surveillance and Response System (GISRS) and partners. Thanks to GISRS, next season’s vaccines have been updated to counter the latest strains of influenza viruses, in turn better protecting communities.

In August 2025, a notably different variant of the A(H3N2) virus emerged (classified as J.2.4.1, also referred to as 'subclade K') and spread rapidly across the globe. This contributed to an earlier start to the influenza season in many countries, with several reporting higher-than-usual levels of activity. 'Subclade K' accounted for the majority of influenza viruses reported across regions.

Overall, influenza A viruses were predominant, with other variants of A(H3N2) and A(H1N1) also noted. Low levels of influenza B viruses (B/Victoria lineage) were detected, with no cases of B/Yamagata lineage viruses recorded since March 2020.

As part of the review, experts also examined influenza viruses that are circulating among animals, especially those that have led to infections in humans. These animal or zoonotic influenza viruses continue to be a major concern due to their potential to cause pandemics.

Since September 23, 2025, after the last consultation, 25 human infections with zoonotic influenza have been reported to the WHO from 6 countries. The majority of these cases were exposed to infected animals or to environments contaminated with influenza viruses. No human-to-human transmission has been reported.

These biannual meetings involve a thorough evaluation of these viruses and the selection of new candidate vaccine viruses (CVVs) that can be quickly utilized to produce vaccines in the event of a pandemic threat. During this meeting, experts advised the creation of a new CVV for an A(H9N2) virus.

an A/Missouri/11/2025 (H1N1)pdm09-like virus;

an A/Darwin/1454/2025 (H3N2)-like virus; and

a B/Tokyo/EIS13-175/2025 (B/Victoria lineage)-like virus.

an A/Missouri/11/2025 (H1N1)pdm09-like virus;

an A/Darwin/1415/2025 (H3N2)-like virus; and

a B/Pennsylvania/14/2025 (B/Victoria lineage)-like virus.

Note to editors

Seasonal influenza (the flu) is an acute respiratory infection caused by influenza viruses. It is prevalent worldwide. There are approximately a billion cases of seasonal influenza each year, with 3 to 5 million cases classified as severe illness. It is estimated to result in 290,000 to 650,000 respiratory deaths annually.

Global influenza surveillance has been conducted through the WHO's Global Influenza Surveillance and Response System (GISRS) since 1952, making it the longest-running global platform for systematic disease surveillance.