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

Abstract

The effectiveness of the 2012/13 trivalent seasonal influenza vaccine (TIV) was assessed using a testnegative 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.

Fluarix quadrivalent vaccine for influenza

“…This could possibly be explained partly by waning of the efficacy. Surveillance studies including 4649 patients show that the efficacy of influenza vaccines reduces from 53% (95% CI: 0-78) within 3 months of vaccination to 12% (95% CI: À31 to 41) after 3 months [19]. On the other hand, other studies suggest the clinical impact of influenza vaccination is clear [36,37].…”

“…Trivalent Fluarix-VB (Victoria lineage B strain) and trivalent Fluarix-YB (Yamagata lineage B strain) are vaccines formulated with the same two influenza A strains (A/H1N1 and A/H3N2) as found in the quadrivalent vaccine, but each has different B strains. These vaccines have been licensed since 2005 and trivalent vaccine efficacy (VE), defined as relative reduction in influenza risk in vaccinated individuals using laboratory-confirmed influenza as the primary outcome, has been reported to be 59% (95% CI: 51-67) over 12 seasons in adults [18] In the UK, the influenza VE at the end of the season 2012-2013 was 51% (95% CI: 34-63) for influenza B and 35% (95% CI: 11-53) for influenza A [19].…”

Use of Computational Matrix Adjustment to Evaluate the Effectiveness of Common Influenza Vaccines against the Emergence of Drift Variants

“…The CDC uses reverse transcription polymerase chain reaction to define vaccine effectiveness (VE) and provide a confidence interval. Based on the CDC website, the acceptable VE lies between 60% to 100% effectiveness, though it is impossible to truly determine vaccine effectiveness without taking into account broader factors such as demography (Andrews et al, 2014).…”

Determining drug efficacy parameters for mathematical models of influenza

“…Influenza mutates rapidly [16] and has the ability to recombine to form new strains [29]. The genetic drift caused by single amino acid mutations can lead to mismatch between the vaccine strains and circulating strains of seasonal influenza [4,11,17]. Particularly concerning are the mutations that confer drug resistance [1,7,10,20,26,28], as they will require a change in treatment strategy.…”