Early estimates of 2016/17 seasonal influenza vaccine effectiveness in primary care in France.

BACKGROUND The ongoing 2016/17 influenza epidemic in France is characterized by the circulation of A(H3N2) viruses, known to cause more severe illness among at risk populations. OBJECTIVES The purpose of our study was to provide early influenza vaccine effectiveness (IVE) estimates for the ongoing influenza epidemic in France and compare these estimates over the six post-pandemic IVE. STUDY DESIGN We used clinical and virological data collected in primary care by the French Sentinelles network. IVE in preventing influenza infection was estimated by the test-negative design method. The screening method was used to estimate IVE in preventing medically-attended influenza-like illness among target groups (<65year with chronic diseases and ≥65 years) since 2010/11 influenza epidemic. RESULTS Early IVE estimates in primary care against influenza A(H3N2) were 48% (95% confidence interval (CI): 22-66) overall and 39% (95% CI: -17 to 69) among elderly (aged 65 and older). In comparison to the last six epidemics, 2016/17 early IVE in preventing influenza-like illness among target groups showed VE estimates higher to those reported during the 2011/12 and 2014/15 epidemics. CONCLUSIONS The moderate 2016/17 IVE estimates were higher than those estimated during influenza A(H3N2) epidemics with vaccine mismatch.