Background: Most studies evaluated the vaccine coverage, but the time of vaccination is important as coverage. This study was conducted to evaluate the Expanded Program of Immunization (EPI) in outskirt of Iranian cities regarding to incidence of delayed vaccination among children less than 4 years. Methods: This cross sectional descriptive study was conducted among children 24-47 months old, living in the suburbs of five metropolises of Iran. Totally, 3610 eligible children selected with proportioned cluster sampling method and data of vaccination card extracted after the interview with children's parents. Delayed incidence rate reported and predictive factors assessed by the Chi square test and Multivariate logistic regression. Results: Overall, 56.6% to 93.2% vaccines were administered out of time. Delayed vaccination incidence with more than one-week delay varies from 5.5% to 74.9% of polio at birth and MMR2 at 18 months, respectively. Mother’s educational level and birth order were the most important predictors of delayed vaccination. Incidence of delayed vaccination was enlarged by increasing birth order and decreased in lower educated mothers. Conclusions: Incidence rate of delayed vaccination is more than expectation. Regarding to high coverage vaccines in Iran, health officers and health policy makers should attempt for ontime vaccination beside of high immunization coverage, especially in slum areas with more concentrated immigrants due to low literature and crowded families. © 2015 Health Hamadan University of Medical Sciences. All rights reserved.

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descriptive research educational status health care policy health care personnel human Measles-Mumps-Rubella Vaccine rural population birth order Iran academic achievement Drug Administration Schedule Cross-Sectional Studies drug administration cluster analysis interview cross-sectional study Humans Poliovirus Vaccines male preschool child poliomyelitis vaccine prediction preventive health service Infant Child, Preschool female Cities Mothers standards Incidence suburban population Article city suburban area mother measles mumps rubella vaccine therapy delay expectation Immunization Programs Delivery of Health Care vaccination immunization health care delivery Child