Influenza virus characterization - Summary Europe, November 2024

It is recommended that vaccines for use in the 2025 SH influenza season contain the following:

Trivalent: Egg‑based Vaccines

• 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.

Trivalent: Cell‑ or recombinant‑based Vaccines

• 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 (egg‑ or cell culture‑ or recombinant‑based vaccines): Above 3 components; and a B/Phuket/3073/2013 (B/Yamagata lineage)‑like virus.

Influenza B/Yamagata‑lineage

No B/Yamagata‑lineage viruses with collection dates after March 2020 have been reported as confirmed detection or sequences released in GISAID as of 30 November 2024.

The absence of confirmed detection of naturally occurring B/Yamagata lineage viruses is indicative of very low risk of infection by B/Yamagata lineage viruses. Therefore, it is the opinion of the WHO influenza vaccine composition advisory committee that inclusion of a B/Yamagata lineage antigen in quadrivalent influenza
vaccines is no longer warranted, and every effort should be made to exclude this component as soon as possible. A continued effort by all NICs of GISRS is required to identify B/Yamagata‑lineage viruses for detailed characterization to determine if there are any in circulation.