Abstract: Objective To analyze the characteristics of the occurrence of the suspected adverse events following immunization (AEFI) in Longbai community from 2007 to 2009 and evaluate the status of the monitoring system and vaccine safety.Methods A descriptive analysis was made on adverse events including common reaction and abnormal reaction based on the data of AEFI individual cases collected by immunization safety monitoring system.Results The average rate of the reported AEFI from 2007 to 2009 was 276.56/100,000,of which,278 were cases of common reaction (accounting for 92.1%),and 24 were cases of abnormal reaction (accounting for 7.9%).There were not vaccination errors,injection reaction,coupled cases or unidentified events reported.The reported AEFI rate of bacterial vaccine was 4.04 times higher than that of viral vaccine.There was higher incidence of AEFI reported in July and August.It was found that the reported AEFI rate in Shanghaiese children was 357.10/100,000,which was higher than that in non-Shanghaiese children.Conclusion The sensitivity and accuracy of AEFI monitoring system is increased as the mode is adopted of active monitoring combined with passive monitoring.