On-time immunization rates among children who enter Chicago public schools

Objective. A primary objective of the Healthy People 2010 initiatives is to increase on-time immunization rates during the first 2 years of life and to decrease racial disparities in coverage. The objective of this study was to determine on-time immunization coverage rates among infants and toddlers stratified by race/ethnicity in a large metropolitan center. Methods. A retrospective cohort study that was based on immunization records in the Chicago Public Schools computerized database was conducted using all 67376 children who completed kindergarten in 2001 and 2002. Results. On-time immunization rates in Chicago public school children are low (31% at 7 months, 32% at 19 months, 59% at 36 months). At 19 months of age and thereafter, Hispanic children had the highest rate of on-time immunization coverage. Among children <48 months old, black children had the lowest rates of up-to-date immunization status. At 48 months of age, the up-to-date rate for black children improved to a rate similar to white children (58%) and by school entry surpassed the up-to-date rate for white children (71%). Compared with the recommended 2, 4, 6, and 15 to 18 months schedule, black children received 4 doses of diphtheria/tetanus/acellular pertussis at a mean age of 10.0, 14.6, 20.4, and 34.5 months of age. In contrast, Hispanic children received the same doses at a mean of 4.5, 7.4, 11.0, and 25.1 month of age. In addition, similar to 25% of black children received the majority of their vaccinations >12 months later than the recommended time intervals. Conclusions. Striking immunization delay still exists during the infant and toddler years. Targeted efforts are needed to increase on-time immunization rates and to decrease racial disparity in immunization coverage.