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The European Medicines Agency (EMA) has issued recommendations for the strains of the influenza virus that vaccine manufacturers should include in vaccines for the prevention of seasonal influenza starting from autumn 2024. These recommendations, based on observations by the World Health Organization (WHO), aim to ensure the effectiveness of influenza vaccines in combating seasonal flu.
EMA’s Emergency Task Force (ETF) has recommended transitioning from quadrivalent to trivalent vaccines, excluding the B/Yamagata component. Quadrivalent vaccines currently protect against four main strains of influenza, including A(H1N1)pdm09, A(H3N2), B/Victoria, and B/Yamagata. However, the B/Yamagata strain has not been detected in circulation since March 2020, likely due to COVID-19 public health measures.
Given the absence of the B/Yamagata virus strain and to optimize vaccine formulations, the ETF recommends removing it from all live-attenuated vaccines for the 2024/2025 season. Additionally, a transition to a trivalent composition for other influenza vaccines is advised for the 2025/2026 season.
The recommendations from the ETF and insights from WHO have led to specific strain recommendations for vaccine manufacturers for the 2024/2025 season:
- Live-attenuated vaccines or egg-based trivalent vaccines should include:
- A/Victoria/4897/2022 (H1N1)pdm09-like virus
- A/Thailand/8/2022 (H3N2)-like virus
- B/Austria/1359417/2021 (B/Victoria lineage)-like virus
- Cell-based trivalent vaccines should include:
- A/Wisconsin/67/2022 (H1N1)pdm09-like virus
- A/Massachusetts/18/2022 (H3N2)-like virus
- B/Austria/1359417/2021 (B/Victoria lineage)-like virus
- Inactivated vaccines may consider producing a quadrivalent vaccine containing:
- The above strains
- B/Phuket/3073/2013 (B/Yamagata lineage)-like virus
These recommendations were endorsed by EMA’s human medicines committee (CHMP) in March 2024. Manufacturers are advised to submit applications to change the composition of centrally authorized seasonal influenza vaccines by June 17, 2024.
Influenza viruses continually evolve, necessitating periodic updates to vaccine strains to maintain effectiveness. EMA’s recommendations aim to ensure that influenza vaccines remain an essential tool in preventing seasonal flu and protecting public health.
