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

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.

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.

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, approximately 25% of black children received the majority of their vaccinations >12 months later than the recommended time intervals.

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.