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 2021/2022 flu season is that all flu vaccines should contain:

Quadrivalent Egg-based Vaccines

• an A/Victoria/2570/2019 (H1N1)pdm09-like virus;
• an A/Cambodia/e0826360/2020 (H3N2)-like virus;
• a B/Washington/02/2019 (B/Victoria lineage)-like virus; and
• a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus

Quadrivalent Cell- or recombinant-based Vaccines

• an A/Wisconsin/588/2019 (H1N1)pdm09-like virus;
• an A/Cambodia/e0826360/2020 (H3N2)-like virus;
• a B/Washington/02/2019 (B/Victoria lineage)-like virus; and
• a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus

It is recommended that trivalent influenza vaccines for use in the 2021 – 2022 northern hemisphere influenza season contain the following:

Egg-based Vaccines

• an A/Victoria/2570/2019 (H1N1)pdm09-like virus;
• an A/Cambodia/e0826360/2020 (H3N2)-like virus; and
• a B/Washington/02/2019 (B/Victoria lineage)-like virus

Cell- or recombinant-based Vaccines

• an A/Wisconsin/588/2019 (H1N1)pdm09-like virus;
• an A/Cambodia/e0826360/2020 (H3N2)-like virus; and
• a B/Washington/02/2019 (B/Victoria lineage)-like virus

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