The World Health Organization (WHO) has announced its recommendations for the viral composition of influenza vaccines for the 2025–2026 influenza season in the northern hemisphere. The recommendations were issued following a four-day meeting on the Composition of Influenza Virus Vaccines, which concluded on Friday. This meeting is held twice annually to ensure vaccines remain effective against evolving influenza viruses.

In a statement published on its website, WHO explained that the recommendations are used by national vaccine regulatory agencies and pharmaceutical companies to develop, produce, and license influenza vaccines for the upcoming season. The periodic update of viruses included in influenza vaccines is essential due to the constant evolution of influenza viruses, including those that circulate and infect humans.

For the 2025–2026 season, WHO recommends that trivalent vaccines for the northern hemisphere include specific strains for egg-based vaccines, cell culture-based vaccines, and recombinant or nucleic acid-based vaccines. The B/Yamagata lineage component for quadrivalent vaccines remains unchanged from previous recommendations.

Egg-Based Vaccines

For egg-based vaccines, WHO recommends the inclusion of the following strains:

  • An A/Victoria/4897/2022 (H1N1)pdm09-like virus;
  • An A/Croatia/10136RV/2023 (H3N2)-like virus; and
  • A B/Austria/1359417/2021 (B/Victoria lineage)-like virus.

Cell Culture-, Recombinant Protein-, or Nucleic Acid-Based Vaccines

For vaccines produced using cell culture, recombinant protein, or nucleic acid technologies, WHO recommends:

  • An A/Wisconsin/67/2022 (H1N1)pdm09-like virus;
  • An A/District of Columbia/27/2023 (H3N2)-like virus; and
  • A B/Austria/1359417/2021 (B/Victoria lineage)-like virus.

Quadrivalent Vaccines

For quadrivalent vaccines, which include an additional B strain, WHO maintains its previous recommendation for the B/Yamagata lineage component:

  • A B/Phuket/3073/2013 (B/Yamagata lineage)-like virus.

The global health agency emphasized that these updates are critical to ensuring the effectiveness of influenza vaccines, as the viruses responsible for seasonal flu are constantly changing. By aligning vaccine composition with the most current and prevalent strains, WHO aims to reduce the impact of influenza outbreaks and protect public health.

The recommendations will guide vaccine manufacturers and regulatory bodies in preparing for the 2025–2026 influenza season, helping to mitigate the spread of the virus and its associated health risks.