Authors reply: influenza vaccine effectiveness: heterogeneity in estimates for the 2012/13 season.

To the editor: We thank Wim van der Hoek and colleagues for their interest in our work [1] and for sharing the preliminary data on influenza vaccine effectiveness (VE) for the 2012/13 season in the Netherlands. When we wrote our article, we emphasised that the findings were based on analysis of data from elderly people mainly admitted to hospital. We cannot make any inference as regards VE among younger, unselected individuals seen in primary healthcare. However, the main public health objective with the influenza vaccination campaign is to prevent morbidity and premature mortality among the frail and the elderly. With this in mind, our observations do have relevance.