Background: Vaccination is a necessary part of the general public health programs and among most value effective medical intervention. Vaccines like different pharmaceutical product don't seem to be entirely risk free; whereas most known facet events area unit gentle and non-serious. However some vaccines are related to terribly rare however serious facet result. So, there's a desire of a police investigation program to watch and record such Events. Aims & Objective: To find out adverse Events following immunizations (AEFI) in youngsters and realize immunizing agent chargeable for them. Material and Methods: A One year prospective immunizing agent safety study was undertaken in 2018 covering a pediatric population of tertiary Care Hospital were administered vaccines. A phone survey of all patients was conducted, comprising of AN initial enter one week and a follow-up enter one year immunizing agent administration date. All AEFI were recorded in immunizing agent Adverse Event reportage System ( VAERS) type. Results: This study was total sample of 4320 children, ranging in age from 6 months to 14 years, 10110 vaccine doses were given. Total 503 AEFI were reported out of a total of 10110 vaccine doses given. The rate of AEFI per thousand doses was 99.2. Out of 2320 children, there were 499 children who were suspected of having at least one AEFI. Hence, the incidence of AEFI was 20.8%. Conclusion: Most of the adverse Events according were gentle and non-serious. Institution of national AEFI info may be a worthy future goal Bangladeshi context.