Modeling the antigenic evolution of seasonal influenza viruses with PREDAC for vaccine strain selection in the season of 2025

Introduction The antigenic evolution of seasonal influenza viruses have been reported to be discontinuous as clusters. Timely identification of antigenic clusters could help for influenza virus vaccine strain selections. Methods Here, we revealed the antigenic evolution of seasonal influenza viruses, including A(H3N2), A(H1N1pdm) and B-Victoria, using our previously developed PREDAC methods, and identified antigenic clusters of seasonal influenza viruses based on existing HA protein sequences in GISAID database. Results During the last six months (2024.2∼2024.7), for the influenza A(H3N2) virus, the antigenic clusters DA21 (A/Darwin/6/2021-like and A/Massachusetts/18/2022-like) continuously dominated and nearly all viruses are antigenic similar to the current vaccine strain A/Massachusetts/18/2022; for the influenza A(H1N1pdm) virus, the antigenic cluster SY21 (A/Sydney/5/2021-like and A/Victoria/4897/2022-like) dominated and nearly all viruses are antigenic similar to the current vaccine strain A/Victoria/4897/2022; for the influenza B-Victoria, antigenic clusters AU21 (B/Austria/1359417/2021-like) dominated and nearly all viruses are antigenic similar to the current vaccine strain B/Austria/1359417/2021. Conclusion The analysis suggests that there is no need to update the vaccine strains in the flu season of 2025 on the aspect of antigenicity.