Effectiveness of trivalent seasonal influenza vaccine in preventing laboratory-confirmed influenza in primary care in the United Kingdom: 2012/13 end of season results

• Published in: Euro surveillance : bulletin européen sur les maladies transmissibles Vol. 19; no. 27; pp. 5 - 13
• Main Authors: Andrews, N, McMenamin, J, Durnall, H, Ellis, J, Lackenby, A, Robertson, C, von Wissmann, B, Cottrell, S, Smyth, B, Moore, C, Gunson, R, Zambon, M, Fleming, D, Pebody, R
• Format: Journal Article
• Language: English
• Published: Sweden Centre Europeen pour la Surveillance Epidemiologique du SIDA (European Centre for the Epidemiological Monitoring of AIDS) 10.07.2014
• Subjects: Adolescent; Adult; Aged; Case-Control Studies; Child; Disease prevention; Effectiveness; Female; Hemagglutination Inhibition Tests; Humans; Influenza; Influenza A Virus, H1N1 Subtype - classification; Influenza A Virus, H1N1 Subtype - genetics; Influenza A Virus, H1N1 Subtype - immunology; Influenza A Virus, H1N1 Subtype - isolation & purification; Influenza A Virus, H3N2 Subtype - classification; Influenza A Virus, H3N2 Subtype - genetics; Influenza A Virus, H3N2 Subtype - immunology; Influenza A Virus, H3N2 Subtype - isolation & purification; Influenza B virus - genetics; Influenza B virus - immunology; Influenza B virus - isolation & purification; Influenza Vaccines - administration & dosage; Influenza Vaccines - immunology; Influenza Vaccines - therapeutic use; Influenza, Human - epidemiology; Influenza, Human - immunology; Influenza, Human - prevention & control; Influenza, Human - virology; Male; Middle Aged; Primary care; Primary Health Care; Reverse Transcriptase Polymerase Chain Reaction; Seasons; Sentinel Surveillance; Sequence Analysis, DNA; Time Factors; Treatment Outcome; United Kingdom - epidemiology; Vaccination - statistics & numerical data; Vaccines
• ISSN: 1560-7917; 1025-496X; 1560-7917
• DOI: 10.2807/1560-7917.ES2014.19.27.20851

The effectiveness of the 2012/13 trivalent seasonal influenza vaccine (TIV) was assessed using a test-negative case-control study of patients consulting primary care with influenza-like illness in the United Kingdom. Strain characterisation was undertaken on selected isolates. Vaccine effectiveness (VE) against confirmed influenza A(H3N2), A(H1N1) and B virus infection, adjusted for age, sex, surveillance scheme (i.e. setting) and month of sample collection was 26% (95% confidence interval (CI): -4 to 48), 73% (95% CI: 37 to 89) and 51% (95% CI: 34 to 63) respectively. There was an indication, although not significant, that VE declined by time since vaccination for influenza A(H3N2) (VE 50% within three months, 2% after three months, p=0.25). For influenza A(H3N2) this is the second season of low VE, contributing to the World Health Organization (WHO) recommendation that the 2013/14 influenza vaccine strain composition be changed to an A(H3N2) virus antigenically like cell-propagated prototype 2012/13 vaccine strain (A/Victoria/361/2011). The lower VE seen for type B is consistent with antigenic drift away from the 2012/13 vaccine strain. The majority of influenza B viruses analysed belong to the genetic clade 2 and were antigenically distinguishable from the 2012/13 vaccine virus B/Wisconsin/1/2010 clade 3. These findings supported the change to the WHO recommended influenza B vaccine component for 2013/14.