The study will be held in the winter of 2005-2006. Groups of vaccinated HCW and not vaccinated HCW will be followed for symptoms suggestive of influenza. For each event a quick through test for influenza A or B will be done and if positive will be confirmed by viral study. Data regarding days of illness, absence from work, therapy etc., will be collected. Effectiveness will be calculated as well as cost/effectiveness of vaccination.
The study will be held in the winter of 2005-2007. The aim is to assess the effectiveness of the influenza vaccine in health care workers (HCW).