Following the onset of the COVID-19 pandemic in 2020, the number of influenza viruses circulating globally fell to historically low numbers. Although influenza A and B/Victoria lineage viruses returned to normal patterns by 2022, B/Yamagata-lineage viruses have not been identified since 2020. The implications of the apparent extinction of this lineage of viruses on vaccine composition, and the risk of their re-introduction into the human population are discussed.
