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. 2022 Sep;27(38):2200720.
doi: 10.2807/1560-7917.ES.2022.27.38.2200720.

Influenza vaccine effectiveness against A(H3N2) during the delayed 2021/22 epidemic in Canada

Shinhye Kim  1 , Erica Sy Chuang  1 , Suzana Sabaiduc  1 , Romy Olsha  2 , Samantha E Kaweski  1 , Nathan Zelyas  3 , Jonathan B Gubbay  4   2 , Agatha N Jassem  5   1 , Hugues Charest  6 , Gaston De Serres  7   8   6 , James A Dickinson  9 , Danuta M Skowronski  5   1
Affiliations

Influenza vaccine effectiveness against A(H3N2) during the delayed 2021/22 epidemic in Canada

Shinhye Kim et al. Euro Surveill. 2022 Sep.

Abstract

Influenza virus circulation virtually ceased in Canada during the COVID-19 pandemic, re-emerging with the relaxation of restrictions in spring 2022. Using a test-negative design, the Canadian Sentinel Practitioner Surveillance Network reports 2021/22 vaccine effectiveness of 36% (95% CI: -38 to 71) against late-season illness due to influenza A(H3N2) clade 3C.2a1b.2a.2 viruses, considered antigenically distinct from the 3C.2a1b.2a.1 vaccine strain. Findings reinforce the World Health Organization's decision to update the 2022/23 northern hemisphere vaccine to a more representative A(H3N2) clade 3C.2a1b.2a.2 strain.

Keywords: A(H3N2); Influenza; clade; observational study; test-negative design; vaccine effectiveness.

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Conflict of interest statement

Conflict of interest: DMS is Principal Investigator on grants received to her institution from the Public Health Agency of Canada and the BCCDC Foundation for Public Health in support of this work. GDS has received grants for investigator-initiated studies unrelated to influenza vaccine from Pfizer, paid to his institution. JBG is a paid consultant scientific editor for GIDEON Informatics, Inc., which is unrelated to the current work. Other authors have no conflicts of interest to declare.

Figures

Figure
Figure
Influenza detections among eligible patients presenting with influenza-like illness by week of specimen collection, Canadian Sentinel Practitioner Surveillance Network, 1 November 2021–30 July 2022 (weeks 44–30: n = 1,087)
See this image and copyright information in PMC

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