The influenza strains to be included in flu vaccines to be used in the upcoming flu season differs according to where the flu vaccines are to be used. If the flu vaccines are for the southern hemisphere the information is released in September each year, whereas for flu vaccines to be used in the northern hemisphere the information is released February time.
In accordance with these timeframes, on 28 February 2020 the World Health Organisation released the strains of influenza that should be included in the vaccine to be used during the 2020-2021 flu season in the Northern hemisphere.
Egg-based Vaccines
an A/Guangdong-Maonan/SWL1536/2019 (H1N1)pdm09-like virus;
an A/Hong Kong/2671/2019 (H3N2)-like virus;
a B/Washington/02/2019 (B/Victoria lineage)-like virus; and
a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus.
Cell- or recombinant-based Vaccines
an A/Hawaii/70/2019 (H1N1)pdm09-like virus;
an A/Hong Kong/45/2019 (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 2020 – 2021 influenza season contain the following:
Egg-based Vaccines
an A/Guangdong-Maonan/SWL1536/2019 (H1N1)pdm09-like virus;
an A/Hong Kong/2671/2019 (H3N2)-like virus; and
a B/Washington/02/2019 (B/Victoria lineage)-like virus.
Cell- or recombinant-based Vaccines
an A/Hawaii/70/2019 (H1N1)pdm09-like virus;
an A/Hong Kong/45/2019 (H3N2)-like virus; and
a B/Washington/02/2019 (B/Victoria lineage)-like virus.
https://www.who.int/influenza/vaccines/virus/recommendations/2020-21_north/en/
https://www.who.int/influenza/vaccines/virus/recommendations/2020_south/en/