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Key Takeaways✦ Atlas AI
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The WHO has recommended the viral composition for the 2026-2027 Northern Hemisphere flu vaccine, guiding manufacturers to match vaccines with evolving influenza strains for optimal protection.
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A new A(H3N2) variant (J.2.4.1 subclade K) emerged in August 2025, contributing to an earlier and more active flu season globally, highlighting the continuous need for vaccine updates.
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The WHO also recommended developing a new A(H9N2) candidate vaccine virus, a proactive measure to enable rapid vaccine production in case of a potential pandemic threat.
Atlas AI
The World Health Organization has issued recommendations on which influenza virus strains should be included in vaccines for the 2026-2027 northern hemisphere flu season. The guidance is intended to help national regulatory agencies and vaccine manufacturers align products with viruses expected to circulate.
Officials said the recommendations draw on global influenza surveillance data. They noted that vaccine strain selection needs regular revision because influenza viruses change over time, and closer matching is intended to improve protection.
Global surveillance points to a new A(H3N2) variant
Experts identified a new A(H3N2) variant classified as J.2.4.1 (subclade K). According to the WHO, it emerged in August 2025 and later spread worldwide.
ATLAS SIGNAL│Public Health│High│3–12 months
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WHO Recommends New Influenza Strains for 2026-27 Northern Hemisphere Vaccines Amidst Evolving Viral Landscape
The World Health Organization (WHO) has released its recommendations for the influenza virus strains to be included in Northern Hemisphere vaccines for the 2026-2027 season. This annual guidance is critical for global public health and vaccine manufacturing, as it aims to align vaccine composition with anticipated circulating strains. The recommendations highlight the continuous evolution of influenza viruses, including the emergence of new A(H3N2) variants and persistently low influenza B activity, underscoring the ongoing need for global surveillance and adaptable vaccine strategies to maintain public health defenses worldwide.
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The WHO said this variant contributed to an earlier and more active influenza season in several regions. Influenza A viruses were reported as the dominant type, with both A(H3N2) and A(H1N1) variants circulating.
Influenza B remains limited; B/Yamagata still absent
Surveillance detected low levels of influenza B viruses from the B/Victoria lineage. The WHO said no B/Yamagata lineage cases have been reported since March 2020.
The organization said the ongoing absence of B/Yamagata in reported surveillance is part of the evidence base considered when advising on vaccine composition, alongside the broader pattern of circulating influenza A and B viruses.
Zoonotic infections reported, with no sustained spread
Since September 2025, 25 human infections with zoonotic influenza have been reported from six countries, the WHO said. Officials said the cases were mainly linked to exposure to infected animals or contaminated environments.
The WHO said there was no evidence of human-to-human transmission in these reports. It added that monitoring such infections remains important because animal-origin influenza viruses can pose risks if they adapt to spread efficiently among people.
Candidate vaccine virus
Separately, the WHO . The organization said such a candidate could support rapid vaccine manufacturing if a pandemic threat were to emerge.
The WHO’s recommendations are advisory and are used by countries and companies as they make decisions on vaccine formulation and production. The organization did not specify how national regulators will implement the guidance, and vaccine availability and timing can vary by market.
