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

N Andrews, J McMenamin, H Durnall, J Ellis, A Lackenby, C Robertson, B von Wissmann, S Cottrell, B Smyth, C Moore, R Gunson, M Zambon, D Fleming, R Pebody

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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.

Original languageEnglish
Pages (from-to)5-13
Number of pages9
Issue number27
Publication statusPublished - 10 Jul 2014


  • adolescent
  • adult
  • aged
  • case-control studies
  • child
  • Great Britain
  • hemagglutination inhibition tests
  • influenza A virus, H1N1 Subtype
  • influenza A virus, H3N2 Subtype
  • influenza B virus
  • influenza vaccines
  • influenza, human
  • primary health care
  • Sentinel Surveillance
  • sequence analysis, DNA
  • treatment outcome
  • vaccination

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