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

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Déclaration de conflit d'intérêts

Declaration of interests MCN received grants from the Foundation for Influenza Epidemiology, Bill & Melinda Gates Foundation, European & Developing Countries Clinical Trials Partnership (EDCTP), Sanofi, AstraZeneca, and Pfizer; received payments or honoraria (for lectures, presentations, speakers bureaus, manuscript writing, or educational events) and support for attending meetings or travel, or both, from Sanofi; and had leadership or fiduciary role from Gavi Board. An unrestricted research grant from NIVEL (the employer) and Sanofi for JP funded the work carried out in this manuscript; JP also received grants or contracts from Sanofi and the Fondation de France; and support for attending meetings or travel, or both, from WHO and Sanofi. The other authors declare no conflicts of interest.