WHO Announces 2026-2027 Flu Vaccine Composition

The World Health Organization (WHO) has announced recommendations for the viral composition of influenza vaccines for the 2026-2027 northern hemisphere influenza season. These recommendations, made following a four-day consultation examining global influenza surveillance data, are crucial for ensuring vaccines are closely matched to circulating viruses and offer the best possible protection against severe illness and death WHO.

Why Vaccine Composition Updates are Necessary

Influenza viruses are constantly changing, necessitating regular updates to vaccine composition. The WHO’s recommendations guide national vaccine regulatory agencies and pharmaceutical companies in developing and producing effective vaccines for each influenza season WHO.

Recommended Vaccine Composition

For the 2026-2027 northern hemisphere influenza season, the WHO recommends the following:

• Egg-based vaccines: An A/Missouri/11/2025 (H1N1)pdm09-like virus
• Cell-based, recombinant proteins or nucleic acids: An A/Missouri/11/2025(H1N1) pdm09 type virus, an A/Darwin/1415/2025 (H3N2)-like virus, and a B/Pennsylvania /14/2025-like virus (B/Victoria lineage) WHO.

Emerging Viral Variants

The WHO has noted that a different variant of the A(H3N2) virus, classified as J.2.4.1 (also known as subclade K), emerged in August 2025 and spread rapidly globally, contributing to an earlier start to the flu season in many countries WHO.

Global Influenza Surveillance

During the recent season, Influenza A viruses predominated, with other variants of A(H3N2) and A(H1N1) also registered. Low levels of influenza B virus (B/Victoria lineage) were detected, with no cases of the B/Yamagata lineage recorded since March 2020 WHO.

Zoonotic Influenza Monitoring

Experts continue to analyze influenza viruses circulating in animals, particularly those causing human infections, due to their pandemic potential. Since the last consultation in September 2025, the WHO has received notification of 25 human infections with zoonotic influenza from six countries. Most cases involved exposure to infected animals or contaminated environments, with no evidence of human-to-human transmission WHO.

Ongoing Research and Pandemic Preparedness

The WHO’s consultations include a detailed evaluation of viruses and the selection of new vaccine candidate viruses (CVVs) for rapid vaccine production in the event of a pandemic threat. At the recent meeting, experts recommended the development of a new CVV for an A(H9N2) virus WHO.

“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. He emphasized that the WHO’s recommendations are based on the diligent work of the Global Influenza Surveillance and Response System (GISRS) and its partners, ensuring that next season’s vaccines are updated to counter the latest strains and better protect communities WHO.