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

Abstract

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.

Keywords: Influenza; Influenza-like illness; Primary care; Vaccine effectiveness.