Interim estimates of 2014/15 vaccine effectiveness against influenza A(H3N2) from Canada’s Sentinel Physician Surveillance Network, January 2015

D M Skowronski; C Chambers; S Sabaiduc; G De Serres; J A Dickinson; A L Winter; S J Drews; K Fonseca; H Charest; J B Gubbay; M Petric; M Krajden; T L Kwindt; C Martineau; A Eshaghi; N Bastien; Y Li

doi:10.2807/1560-7917.ES2015.20.4.21022

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Interim estimates of 2014/15 vaccine effectiveness against influenza A(H3N2) from Canada’s Sentinel Physician Surveillance Network, January 2015
D M Skowronski^1,2 , C Chambers¹ , S Sabaiduc¹ , G De Serres^3,4,5 , J A Dickinson⁶ , A L Winter⁷ , S J Drews^8,9 , K Fonseca^6,10 , H Charest³ , J B Gubbay^7,11 , M Petric² , M Krajden^1,2 , T L Kwindt^1,2 , C Martineau³ , A Eshaghi⁷ , N Bastien¹² , Y Li^12,13
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Affiliations: ¹ British Columbia Centre for Disease Control, Vancouver, Canada ² University of British Columbia, Vancouver, Canada ³ Institut National de Santé Publique du Québec (National Institute of Health of Quebec), Québec, Canada ⁴ Laval University, Quebec, Canada ⁵ Centre Hospitalier Universitaire de Québec (University Hospital Centre of Quebec), Québec, Canada ⁶ University of Calgary, Calgary, Canada ⁷ Public Health Ontario, Toronto, Canada ⁸ University of Alberta, Edmonton, Canada ⁹ Alberta Provincial Laboratory, Edmonton, Canada ¹⁰ Alberta Provincial Laboratory, Calgary, Canada ¹¹ University of Toronto, Toronto, Canada ¹² National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Canada ¹³ University of Manitoba, Winnipeg, Canada

Correspondence:
D Skowronski
danuta.skowronski bccdc.ca
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Citation style for this article: Skowronski D M, Chambers C, Sabaiduc S, De Serres G, Dickinson J A, Winter A L, Drews S J, Fonseca K, Charest H, Gubbay J B, Petric M, Krajden M, Kwindt T L, Martineau C, Eshaghi A, Bastien N, Li Y. Interim estimates of 2014/15 vaccine effectiveness against influenza A(H3N2) from Canada’s Sentinel Physician Surveillance Network, January 2015. Euro Surveill. 2015;20(4):pii=21022. https://doi.org/10.2807/1560-7917.ES2015.20.4.21022 Received: 21 Jan 2015

Abstract

The 2014/15 influenza season to date in Canada has been characterised by predominant influenza A(H3N2) activity. Canada's Sentinel Physician Surveillance Network (SPSN) assessed interim vaccine effectiveness (VE) against medically attended, laboratory-confirmed influenza A(H3N2) infection in January 2015 using a test-negative case-control design. Of 861 participants, 410 (48%) were test-positive cases (35% vaccinated) and 451 (52%) were test-negative controls (33% vaccinated). Among test-positive cases, the majority (391; 95%) were diagnosed with influenza A, and of those with available subtype information, almost all influenza A viruses (379/381; 99%) were A(H3N2). Among 226 (60%) A(H3N2) viruses that were sequenced, 205 (91%) clustered with phylogenetic clade 3C.2a, considered genetically and antigenically distinct from the 2014/15 A/Texas/50/2012(H3N2)-like clade 3C.1 vaccine reference strain, and typically bearing 10 to 11 amino acid differences from the vaccine at key antigenic sites of the haemagglutinin protein. Consistent with substantial vaccine mismatch, little or no vaccine protection was observed overall, with adjusted VE against medically attended influenza A(H3N2) infection of ?8% (95% CI: ?50 to 23%). Given these findings, other adjunct protective measures should be considered to minimise morbidity and mortality, particularly among high-risk individuals. Virus and/or host factors influencing this reduced vaccine protection warrant further in-depth investigation. .