Flu Vaccine Update: New Strain Focus and Pandemic Preparedness
The World Health Organization (WHO) has announced recommendations for the 2026-2027 northern hemisphere influenza vaccine composition. This year’s update includes the A(H1N1)pdm09, A(H3N2), and B/Victoria viruses. Significantly, experts are also recommending development of a candidate vaccine virus (CVV) for A(H9N2), recognizing its potential to rapidly produce vaccines should it pose a pandemic threat.
The Evolving Threat of Influenza
Influenza viruses are in constant flux, necessitating regular vaccine updates. The WHO’s recommendations guide vaccine manufacturers and regulatory agencies worldwide, aiming to ensure the best possible match between vaccines and circulating viruses. This proactive approach is crucial for maximizing protection against severe illness and death.
Surveillance data reveals that influenza viruses circulating in animals, particularly those infecting humans, remain a significant concern. These zoonotic viruses have the potential to trigger pandemics. Since September 23, 2025, the WHO has been notified of 25 human infections with zoonotic influenza from six countries. These cases involved exposure to infected animals or contaminated environments, though no human-to-human transmission has been reported.
A(H3N2) Variant and Early Flu Season
In August 2025, a distinct variant of the A(H3N2) virus (J.2.4.1, or subclade K) emerged and spread globally. This contributed to an earlier-than-usual start to the flu season in many countries, with some regions experiencing higher-than-normal activity levels. Influenza A viruses were predominant, with other A(H3N2) and A(H1N1) variants also detected. Low levels of influenza B virus (B/Victoria lineage) were observed, with no cases of the B/Yamagata lineage reported since March 2020.
Focus on A(H9N2): A Potential Pandemic Risk
While currently not demonstrating sustained human-to-human transmission, the A(H9N2) virus is under close scrutiny. Avian influenza A (H9N2) viruses have been infecting humans since 1999, typically through direct contact with infected birds. The WHO’s proactive development of a candidate vaccine virus for A(H9N2) demonstrates a commitment to pandemic preparedness. Low pathogenic avian influenza A (H9N2) viruses are currently endemic in poultry populations across Africa, Asia, the Middle East, and Europe.
Did you know? Influenza A viruses have a natural reservoir in wild aquatic birds, making complete eradication impossible. In other words ongoing surveillance and adaptation are essential.
Global Impact of Influenza
Influenza is a common respiratory infection worldwide, causing an estimated 3 to 5 million severe cases and 290,000 to 650,000 respiratory deaths annually, from an estimated 1 billion cases each year. The interconnectedness of the world means shared risks require shared action, as emphasized by WHO Director-General Dr. Tedros Adhanom Ghebreyesus.
FAQ: Influenza and Vaccine Updates
- What viruses are included in the 2026-2027 flu vaccine? The vaccine will include A(H1N1)pdm09, A(H3N2), and B/Victoria.
- Why is A(H9N2) being monitored? While it doesn’t currently spread easily between people, A(H9N2) has the potential to cause a pandemic.
- What is a candidate vaccine virus (CVV)? A CVV is a virus developed for rapid vaccine production if a pandemic threat emerges.
- How often are flu vaccines updated? Flu vaccines are updated annually to match circulating viruses.
Pro Tip: Staying informed about the latest influenza updates and getting vaccinated annually are the best ways to protect yourself and your community.
Learn more about influenza from the World Health Organization.
What are your biggest concerns about the upcoming flu season? Share your thoughts in the comments below!
