Letter to the editor: Influenza vaccine effectiveness: heterogeneity in estimates for the 2012/13 season

摘要

VE and in which the study popula- tion consists of people tested for suspected influenza [4]. Those with a positive test for influenza virus are cases and those with a negative test are controls. VE is then calculated based on the influenza vaccination status of cases and controls. Most studies estimate VE from GP networks, in which patients presenting with influenza-like illness (ILI) are swabbed for surveillance purposes. In the Netherlands, we routinely estimate VE with the test-negative approach from the senti- nel GP network of the NIVEL Netherlands Institute for Health Services Research [5]. The information it col- lects is indicative only, as the number of swabs from ILI patients is often too low to obtain robust estimates.