Will Flu Shots Be More Effective in 2026-2027

The World Health Organization (WHO) today announced the recommended viral composition for influenza vaccines for the northern hemisphere influenza season of 2026-2027. This update aims to match the circulating strains better, enhancing protection against seasonal flu outbreaks.

For egg-based vaccines, the WHO recommends the following:

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

- An A/Darwin/1454/2025 (H3N2)-like virus

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

For vaccines based on cell culture, recombinant protein, or nucleic acid, the WHO recommends:

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

- An A/Darwin/1415/2025 (H3N2)-like virus

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

The WHO reported that influenza A viruses were predominant, with other A(H3N2) and A(H1N1) variants also observed. Low levels of influenza B viruses (B/Victoria lineage) were detected, and no cases of B/Yamagata lineage viruses have been recorded since March 2020.

"Season after season, constantly evolving influenza viruses circulate globally, reminding us how interconnected our world is. Shared risks require shared action," stated Dr. Tedros Adhanom Ghebreyesus, WHO Director-General, in a press release on February 27, 2026.

These WHO recommendations guide national vaccine regulatory agencies and pharmaceutical companies worldwide in the development, production, and licensing of influenza vaccines for the upcoming season. This process ensures that vaccines are closely matched to the viruses expected to circulate, providing the best possible protection against severe illness and death.

To highlight the ongoing importance of flu vaccination, data from the U.S. Centers for Disease Control and Prevention (CDC) on vaccine effectiveness over the last three completed seasons in the USA show varying but significant levels of protection.

For the 2022-2023 season, the overall adjusted vaccine effectiveness was estimated at 30% (95% CI: -9%, 54%).

This improved to 44% (95% CI: 36%, 51%) in 2023-2024, and reached 56% (95% CI: 54%, 58%) in 2024-2025.

No official data has been posted for the 2025-2026 flu season.

These CDC figures underscore the vaccine's role in reducing flu-related hospitalizations and outpatient visits, even as effectiveness can fluctuate based on virus match and population factors.

As global travel increases, health experts emphasize the importance of timely vaccination, particularly for international travelers who may encounter diverse strains when visiting a different hemisphere.

The WHO's latest guidance helps travel clinics recommend flu shots amid an ever-changing influenza landscape.