KEYWORDS:
WIC, immunizations

BACKGROUND:
WIC serves a large proportion of Chicago infants but some do not remain in WIC after age one year.

OBJECTIVE(S):
To determine if children who remained active at selected WIC/immunization- linked sites after their first birthday were more likely to be well-immunized at ages 18 and 24 months compared to those who dropped out.

METHOD(S):
Four Chicago WIC sites that reported using voucher incentives were chosen for this retrospective cohort study. Data on WIC visits were obtained from the Illinois Department of Human Services. The initial cohort (n=1142) consisted of children born from 7/1/97 to 9/30/97 who stayed within the 4 sites for their WIC visits. The cohort was divided into 2 groups: active (A) group (n=528, 46%) had a WIC visit on or after their first birthday, inactive (INA) group (n=614, 54%) had their last WIC visit before their first birthday. Children were randomly ordered within the groups and enrolled through home visits.

RESULT(S):
Two-hundred children with reliable immunization records were used in the analysis. Enrollment was attempted for 492 other children before sample size was reached; most of these could not be located. At age 18 months, 65 (84%) of 77 A children had received MMR, compared to 82 (67%) of 123 INA children (RR=1.27; 95% CI=1.08,1.48). At age 24 months, 64 (83%) A children had received 4 DPT:1 MMR:3 Hib compared to 64 (52%) INA children (RR=1.60, 95%CI=1.31,1.95).

CONCLUSIONS(S):
In this cohort, children active in WIC after their first birthday were more likely to be well-immunized at ages 18 and 24 months compared to those who were no longer active. Chicago children who drop out of WIC may represent those at highest risk for underimmunization and may require special strategies to improve coverage.

LEARNING OBJECTIVES:
Describe risk for underimmunization in children who dropped out of WIC.