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Influenza vaccine effectiveness against A(H3N2) during the delayed 2021/22 epidemic in Canada
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View Affiliations Hide AffiliationsDanuta M Skowronskidanuta.skowronski bccdc.ca
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Citation style for this article: . Influenza vaccine effectiveness against A(H3N2) during the delayed 2021/22 epidemic in Canada. Euro Surveill. 2022;27(38):pii=2200720. https://doi.org/10.2807/1560-7917.ES.2022.27.38.2200720 Received: 10 Sept 2022; Accepted: 21 Sept 2022
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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.
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