Surveillance system of vaccine adverse events and local data analysis--the experience in a middle-sized city in Brazil, 1999-2001.

We reviewed all vaccine adverse events (VAE) notified in a middle-sized Brazilian city (n=247) to the National Immunisation Program between January 1999 and December 2001. Vaccine doses used in that period were considered for rate estimates. Aspects of the surveillance system (SS) and their influences on collected data were considered, searching for contributions of local data analysis to investigation of VAE and to the monitoring of vaccine safety. Notification rates in our study were higher when compared to national data. Changes in the notification pattern were observed following vaccination campaign periods. An increase in aseptic meningitis cases temporally associated to yellow fever vaccine was detected. The analysis of local data provided information unperceived in national consolidated data. Through this analysis we detected: events related to application technique and handling; people's perception changes on VAE; and the local SS's ability to raise new hypothesis. We suggested changes to the notification form regarding data entry criteria and analysis.