INTERACTION OF SOCIOECONOMIC-STATUS AND PROVIDER PRACTICES AS PREDICTORS OF IMMUNIZATION COVERAGE IN VIRGINIA CHILDREN

Objective. To describe the pattern of immunization in the cohort of ch ildren who entered public schools in Virginia in 1992. Design. This wa s a historic cohort study using stratified cluster sampling. Three str ata were created based on the socioeconomic status (SES) of the childr en in the catchment area of each public school in Virginia. Setting. T he random sample included public elementary schools throughout Virgini a. Participants. Immunization records were obtained for a randomly sel ected cohort of 2519 first-grade children in Virginia. Outcome Measure s. Age at completion of recommended childhood vaccines was determined from birth to school entry by SES, race, and population density. Provi der practices were assessed by ascertaining missed opportunities for s imultaneous administration of vaccinations according to recommended sc hedules. Results. Although immunization completion rates were high at school entry, low levels of immunization coverage were found in all ar eas of Virginia at 24 months of age regardless of SES (as measured by per capita income), population density, or race. However, under-immuni zation was more severe for poor children in urban areas (42.3% of chil dren in low-SES urban areas were age-appropriately immunized at 24 mon ths of age versus 64.0% in children in high-SES rural areas). By multi variate logistic regression, race and gender were not predictors of wh ich children were appropriately immunized at 2 years of age after adju sting for the following: SES, population density, receiving the first DTP (diphtheria, tetanus, and pertussis) or OPV (oral polio) vaccinati on after 3 months of age, and failure to have the first DTP administer ed simultaneously with the first OPV or the second DTP administered si multaneously with the second OPV. Receiving the first DTP or OPV vacci nation after 3 months of age and failure to have the first and second DTP and OPV administered simultaneously were the strongest predictors of not being age-appropriately immunized at 2 years of age. The effect of failure to vaccinate simultaneously on predicting vaccination cove rage at 2 years of age was strongly modified by SES. Children who atte nded schools located in census tracts with per capita incomes less tha n $10 600 and who did not have the first and second doses of DTP and O PV administered simultaneously were 33.19 times more likely not to be age-appropriately immunized at 2 years of age compared with children w ho attended schools located in census tracts with per capita incomes g reater than $18 800 and who received the first and second doses of DTP and OPV simultaneously (95% confidence interval: 18.29 to 60.22). Con clusions. Although beginning the immunization schedule at the recommen ded age was crucial to appropriate vaccination later in life, provider practices were important predictors of under-immunization. Failure to administer vaccinations simultaneously strongly influenced poorer chi ldren in Virginia. Serious delays in vaccine administration were obser ved not only for poor children in urban areas, but also in all areas o f Virginia before school entry.