Influenza vaccine effectiveness (VE) has to be estimated anew for every season to explore vaccines’ protective effect in the population. We report VE estimates against laboratory-confirmed influenza A(H1N1)pdm09, A(H3N2) and influenza B among children aged 2-17 years, using test-negative design. Pooled data from two German federal states’ surveillance systems for acute respiratory illness from week 40/2012 to 20/2016 was used, yielding a total of 10 627 specimens. Odds ratios and 95% confidence intervals (95% CIs) for the association between laboratory-confirmed influenza and vaccination status were calculated by multivariate logistic regression adjusting for age, sex, illness onset and federal state. VE was estimated as 1-Odds Ratio. Overall adjusted VE was 33% (95% CI: 24·3-40·7). A strong variation of VE between the seasons and subtypes was observed: highest season- and subtype-specific VE of 86·2% (95% CI: 41·3-96·7) was found against A(H1N1)pdm09 in 7-17-year-olds in 2015/16. Low estimates of VE were observed against A(H3N2) in any season, e.g. 1·5% (95% CI: -39·3-30·3) in 2014/15. Estimates showed a tendency to higher VE among 7-17-year-old children, but differences were not statistically significant. Although our findings are common in studies estimating influenza VE, we discussed several explanations for observed low VE.
【저자키워드】 Epidemiology, vaccine effectiveness, routine surveillance data, test-negative design, Influenza (seasonal),