The periodic replacement of virus strains contained in influenza vaccine is necessary because of the constant evolution of influenza viruses, which can change their antigenic and genetic characteristics. The World Health Organization (WHO) recommends the following influenza vaccine composition information.
Northern Hemisphere 2023 – 2024
The WHO recommends that trivalent vaccines for use in the 2023-2024 northern hemisphere influenza season contain the following:
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.
Cell culture- 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
For quadrivalent egg- or cell culture-based or recombinant vaccines for use in the 2023-2024 northern hemisphere influenza season, the WHO recommends inclusion of the following as the B/Yamagata lineage component:
• a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus.
More information
WHO (24 February 2023) Recommended composition of influenza virus vaccines for use in the 2023-2024 northern hemisphere influenza season
WHO (24 February 2023) Frequently asked questions
WHO (24 February 2023) Genetic and antigenic characteristics of zoonotic influenza A viruses and development of candidate vaccine viruses for pandemic preparedness
Southern Hemisphere 2024
The WHO recommends that trivalent vaccines for use in the 2024 southern hemisphere influenza season contain the following:
Egg-based vaccines
• an A/Victoria/4897/2022 (H1N1)pdm09-like virus;
• an A/Thailand/8/2022 (H3N2)-like virus; and
• a B/Austria/1359417/2021 (B/Victoria lineage)-like virus.
Cell culture- or recombinant-based vaccines
• an A/Wisconsin/67/2022 (H1N1)pdm09-like virus;
• an A/Massachusetts/18/2022 (H3N2)-like virus; and
• a B/Austria/1359417/2021 (B/Victoria lineage)-like virus.
For quadrivalent egg- or cell culture-based or recombinant vaccines for use in 2024 southern hemisphere influenza season, the WHO recommends inclusion of the following B/Yamagata lineage component:
• a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus.
More information
WHO. (29 September 2023) Recommended composition of influenza virus vaccines for use in the 2024 southern hemisphere influenza season
WHO. (29 September 2023) Frequently asked questions
WHO. (29 September 2023) Genetic and antigenic characteristics of zoonotic influenza A viruses and development of candidate vaccine viruses for pandemic preparedness
(Updated 22 November 2023)