Salman Khazaei - Department of Epidemiology & Biostatistics, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran.
Shahab Rezaeian - Social Development & Health Promotion Research Center, Gonabad University of Medical Sciences, Gonabad, Iran
Mohsen Razani - Faculty Member of Nursing Department, Broujerd Branch, Islamic Azad University, Broujerd, Iran.
Ali Zahiri - Expert of Public Health, Deputy of Health, Hamadan University of Medical Sciences, Hamadan, Iran.

Background: The surveillance of adverse events following immunization (AEFI) is essential to improve high standard of vaccine safety, and maintain public trust in immunization programs. This study aimed to determine the AEFI and their related factors in children. Materials and Methods: This cross-sectional study including all children under 7- year of age, in Hamadan Province, the West of Iran, in 2014. All of the AEFI related with Bacille Calmette-Guérin (BCG), Diphtheria, Pertussis, and Tetanus (DPT), Measles, Mumps, and Rubella (MMR) vaccines were obtained from the documented record-based by Health Centers, in Hamadan province. Results: From a total of 239,204 doses administered, 284 AEFI were notified (11.8 per 10,000 doses). The proportion of AEFI was more frequently reported from Health Houses than Health Centers (60.2 vs. 37.0, P<0.05). The most frequently AEFI reported was lymphadenitis (31.4%), followed by hyperpyrexia (17%), and severe local reaction (13.5%). Most frequently AEFI reported were related to vaccination reaction (74.7%) and programmatic errors (12.7%). Also, for incidence of lymphadenitis, the overall median time from vaccination to adverse event was 2 days (IQR: 2-15) and the highest median time was 15 days (IQR: 15-571). Conclusion: Our study shown, an increased risk of AEFI in the region and point out that the programmatic error still needs to be considered. Accordingly, the more activities need to be consolidated to reduce the adverse effect. This study assessed the different aspects of AEFI which may help policymakers to improve the immunization programs.

Adverse events, Children, Immunization Programs, Vaccination, Iran