It. Williams et al., INTERACTION OF SOCIOECONOMIC-STATUS AND PROVIDER PRACTICES AS PREDICTORS OF IMMUNIZATION COVERAGE IN VIRGINIA CHILDREN, Pediatrics, 96(3), 1995, pp. 439-446
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.