Probable extinction of influenza B/Yamagata and its public health implications: a systematic literature review and assessment of global surveillance databases

Early after the start of the COVID-19 pandemic, the detection of influenza fl uenza B/Yamagata cases decreased globally. Given the potential public health implications of this decline, in this Review, we systematically analysed data on influenza fl uenza B/Yamagata virus circulation (for 2020-23) - 23) from multiple complementary sources of information. We identified fi ed relevant articles published in PubMed and Embase, and data from the FluNet, Global Initiative on Sharing All Influenza fl uenza Data, and GenBank databases, webpages of respiratory virus surveillance systems from countries worldwide, and the Global Influenza fl uenza Hospital Surveillance Network. A progressive decline of influenza fl uenza B/Yamagata detections was reported across all sources, in absolute terms (total number of cases), as positivity rate, and as a proportion of influenza fl uenza B detections. Sporadically reported influenza fl uenza B/Yamagata cases since March, 2020 were mostly vaccine-derived, attributed to data entry errors, or have yet to be definitively fi nitively confirmed. fi rmed. The likelihood of extinction necessitates a rapid response in terms of reassessing the composition of influenza fl uenza vaccines, enhanced surveillance for B/Yamagata, and a possible change in the biosafety level when handling B/Yamagata viruses in laboratories.