Interim estimates of 2015/16 vaccine effectiveness against influenza A(H1N1)pdm09, Canada, February 2016

• Published in: Euro surveillance : bulletin européen sur les maladies transmissibles Vol. 21; no. 11; p. 30168
• Main Authors: Chambers, Catharine, Skowronski, Danuta M, Sabaiduc, Suzana, Winter, Anne Luise, Dickinson, James A, De Serres, Gaston, Gubbay, Jonathan B, Drews, Steven J, Martineau, Christine, Eshaghi, Alireza, Krajden, Mel, Bastien, Nathalie, Li, Yan
• Format: Journal Article
• Language: English
• Published: Sweden Centre Europeen pour la Surveillance Epidemiologique du SIDA (European Centre for the Epidemiological Monitoring of AIDS) 17.03.2016
• Subjects: Adolescent; Adult; Aged; Canada - epidemiology; Case-Control Studies; Child; Child, Preschool; Female; Glycosylation; Hemagglutination Inhibition Tests; Humans; Infant; Influenza A Virus, H1N1 Subtype - genetics; Influenza A Virus, H1N1 Subtype - immunology; Influenza A Virus, H1N1 Subtype - isolation & purification; Influenza Vaccines - administration & dosage; Influenza Vaccines - immunology; Influenza, Human - diagnosis; Influenza, Human - epidemiology; Influenza, Human - prevention & control; Influenza, Human - virology; Middle Aged; Mutation; Outcome Assessment (Health Care); Proteins; Reverse Transcriptase Polymerase Chain Reaction; Seasons; Sentinel Surveillance; Swine flu; Vaccination - statistics & numerical data; Vaccine Potency; Vaccines; Viruses; Canada; effectiveness; influenza; influenza virus; influenza-like illness - ILI; vaccines and immunisation; vaccine-preventable diseases
• ISSN: 1560-7917; 1025-496X; 1560-7917
• DOI: 10.2807/1560-7917.es.2016.21.11.30168

Using a test-negative design, the Canadian Sentinel Practitioner Surveillance Network (SPSN) assessed interim 2015/16 vaccine effectiveness (VE) against influenza A(H1N1)pdm09 viruses. Adjusted VE showed significant protection of 64% (95% confidence interval (CI): 44-77%) overall and 56% (95%CI: 26-73%) for adults between 20 and 64 years-old against medically attended, laboratory-confirmed A(H1N1)pdm09 illness. Among the 67 A(H1N1)pdm09-positive specimens that were successfully sequenced, 62 (> 90%) belonged to the emerging genetic 6B.1 subclade, defined by S162N (potential gain of glycosylation) and I216T mutations in the haemagglutinin protein. Findings from the Canadian SPSN indicate that the 2015/16 northern hemisphere vaccine provided significant protection against A(H1N1)pdm09 illness despite genetic evolution in circulating viruses.