Effectiveness of seasonal influenza vaccine in preventing laboratory-confirmed influenza in primary care in the United Kingdom : 2014/15 end of season results

Pebody, R. and Warburton, F. and Andrews, N. and Ellis, J. and Von Wissmann, B. and Robertson, C. and Yonova, I. and Cottrell, S. and Gallagher, N. and Green, H. and Thompson, C. and Galiano, M. and Marques, D. and Gunson, R. and Reynolds, A. and Moore, C. and Mullett, D. and Pathirannehelage, S. and Donati, M. and Johnston, J. and De Lusignan, S. and McMenamin, J. and Zambon, M. (2015) Effectiveness of seasonal influenza vaccine in preventing laboratory-confirmed influenza in primary care in the United Kingdom : 2014/15 end of season results. Eurosurveillance, 20 (36). 1. ISSN 1025-496X

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    Abstract

    The 2014/15 influenza season in the United Kingdom (UK) was characterised by circulation of predominantly antigenically and genetically drifted influenza A(H3N2) and B viruses. A universal paediatric influenza vaccination programme using a quadrivalent live attenuated influenza vaccine (LAIV) has recently been introduced in the UK. This study aims to measure the end-of-season influenza vaccine effectiveness (VE), including for LAIV, using the test negative case–control design. The overall adjusted VE against all influenza was 34.3% (95% confidence interval (CI) 17.8 to 47.5); for A(H3N2) 29.3% (95% CI: 8.6 to 45.3) and for B 46.3% (95% CI: 13.9 to 66.5). For those aged under 18 years, influenza A(H3N2) LAIV VE was 35% (95% CI: −29.9 to 67.5), whereas for influenza B the LAIV VE was 100% (95% CI:17.0 to 100.0). Although the VE against influenza A(H3N2) infection was low, there was still evidence of significant protection, together with moderate, significant protection against drifted circulating influenza B viruses. LAIV provided non-significant positive protection against influenza A, with significant protection against B. Further work to assess the population impact of the vaccine programme across the UK is underway.