EMA has issued recommendations for the influenza virus strains that vaccine manufacturers should include in vaccines for the prevention of seasonal influenza from autumn 2024.

Every year, EMA issues EU recommendations for the composition of seasonal influenza vaccines on the basis of observations by the World Health Organization (WHO) which are informed by regular monitoring activities on the prevalence and characteristics of different influenza viruses worldwide.

Based on this data EMA’s Emergency Task Force (ETF) has issued a statement recommending a transition from quadrivalent to trivalent vaccines that do not include the B/Yamagata component.

Currently, most authorised influenza vaccines are quadrivalent, which means that they are formulated to protect against the four main strains of influenza responsible for seasonal flu, A(H1N1)pdm09 and A(H3N2), B/Victoria and B/Yamagata. However, the B/Yamagata strain of the influenza B virus has not been detected in circulation since March 2020. This is thought to be due in part to the public health measures put in place to limit the spread of COVID-19 during the pandemic. Influenza B viruses are responsible for a quarter of annual influenza infections.

Given that the B-Yamagata virus strain no longer seems to pose a threat to public health, it is not necessary to include it in the formulation of influenza vaccines. The ETF recommends that this strain should ideally be removed from all live-attenuated vaccines from the 2024/2025 season. In the interest of guaranteeing vaccine supplies for the coming vaccination campaign, the transition to a trivalent composition for all other influenza vaccines should be completed for the 2025/2026 season.

Taking into account the statement from the ETF and the insights and recommendation from the WHO, the EMA’s ad hoc Influenza Working Group, has issued the following strain recommendations for this year.

Manufacturers of live-attenuated vaccines, or egg-based trivalent vaccines should include these three virus strains for the 2024/2025 season:

an A/Victoria/4897/2022 (H1N1)pdm09-like virus;
an A/Thailand/8/2022 (H3N2)-like virus;
a B/Austria/1359417/2021 (B/Victoria lineage)-like virus.
Manufacturers of cell-based trivalent vaccines should include these three virus strains for the 2024/2025 season:

an A/Wisconsin/67/2022 (H1N1)pdm09-like virus;
an A/Massachusetts/18/2022 (H3N2)-like virus;
a B/Austria/1359417/2021 (B/Victoria lineage)-like virus.
Manufacturers of inactivated vaccines can consider producing a quadrivalent vaccine containing two influenza B virus strains for the 2024/2025 season. In that case a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus in addition to the strains mentioned above is considered appropriate.

The recommendations for the influenza season 2024/2025 were endorsed by EMA's human medicines committee (CHMP) at its March 2024 meeting.

Influenza viruses continuously change and evolve. The periodic replacement of the virus strains contained in influenza vaccines is therefore necessary to keep the vaccines effective.

The Agency recommends that marketing authorisation holders submit applications to change the composition of centrally authorised seasonal influenza vaccines by 17 June 2024.

https://www.ema.europa.eu/en/news/eu-recommendations-2024-2025-seasonal-flu-vaccine-composition