 Data routinely collected as part of clinical consultations in primary care will be extracted from nine General Practitioner GP practices in order to estimate medically attended Adverse Events of Interest AEIs, for people who have received an influenza vaccine. This study will also actively follow patients who were exposed to seasonal influenza vaccination for 7 days in three of the nine GP practices using a customised card-based adverse drug reaction reporting system, in order to determine whether a more active approach to surveillance can capture higher rates of AEIs. 