What strains does the seasonal Flu vaccine protect against? 

Each flu season, experts from around the world help formulate standardised recommendations for flu vaccine manufacture, based on surveillance of the predominant strains around the world.

The WHO recommendation for the Northern Hemisphere 2023/2024 flu season is that all flu vaccines should contain:

Quadrivalent Egg-based Vaccines

• an A/Victoria/4897/2022 (H1N1)pdm09-like virus;
• an A/Darwin/9/2021 (H3N2)-like virus: and
• a B/Austria/1359417/2021 (B/Victoria lineage)-like virus.
• a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus.

Quadrivalent Cell- or recombinant-based Vaccines

• an A/Wisconsin/67/2022 (H1N1)pdm09-like virus;
• an A/Darwin/6/2021 (H3N2)-like virus; and
• a B/Austria/1359417/2021 (B/Victoria lineage)-like virus
• a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus.

You can find the full WHO flu vaccination strain specifications here.