There are many different flu viruses, and they are constantly changing. The composition of US flu vaccines is reviewed annually and updated as needed to match circulating flu viruses. This season, all flu vaccines will be designed to protect against the four viruses that research indicates will be most common. Each year, the Food and Drug Administration’s Vaccines and Related Biological Products Advisory Committee (VRBPAC) makes the recommendation for the flu vaccine composition for US flu vaccines.

For 2021-2022, recommendations were made for egg-based, cell-based, and recombinant flu vaccines as listed below:

Egg-based vaccine composition recommendations:

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

Cell- or recombinant-based vaccine composition recommendations:

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

These recommendations include two updates compared with 2020-2021 US flu vaccines. Both the influenza A(H1N1) and the influenza A(H3N2) vaccine virus components were updated. Compared with the Southern Hemisphere flu vaccine recommendation, this recommendation represents one update and that is to the influenza A(H3N2) component.

For more information, visit Influenza Vaccine for the 2021-2022 Season | FDAexternal icon

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