BACKGROUND:
Even though childhood immunization rates in the United States are at record highs, disparities in immunization coverage still remain. The Oregon Health Plan, an expanded Medicaid program, plays a valuable role in the immunization status of children at-risk.

OBJECTIVE:
To describe immunization-initiation patterns in a cohort of infants covered by the Oregon Health Plan and to identify demographic and health care system factors associated with immunization status among mothers and their infants at three months of age.

METHOD:
Immunization data for babies born 2000-2001 were obtained from the Oregon statewide registry, and the medical records of those infants and their mothers covered by the Oregon Health Plan. Factors significantly associated with immunization initiation were entered into a logistic regression model to adjust for confounding and to determine odds ratios.

RESULT:
The majority of the 39,708 infants (84%) had received their first immunization by three months of age. However, one-in-six infants had not yet initiated immunization. Five factors were independently predictive of immunization initiation: age of infant when OHP coverage began (OR = 2.1, 95% CI = 1.7, 2.5); mother covered by OHP (OR = 1.5, 95% CI = 1.4, 1.6); OHP eligibility category (OR = 1.2, 95% CI = 1.1, 1.3); race/ethnicity of infant (OR = .94, 95% CI = .92, .96); and mothers' number of births (OR = .83, 95% CI = .74, .95).

CONCLUSION:
The gap between immunization rates in the Medicaid population and the general population can be reduced by assuring the mother's coverage during pregnancy and the infant's coverage beginning at birth. Elimination of the cost barrier alone does not guarantee timely immunization initiation. There is much more to learn about what accounts for immunization disparities—even within the first three months of life.

LEARNING OBJECTIVES:
At the conclusion of this session, the participant will have a clear understanding of the predictors of immunization initiation among infants in the Oregon Health Plan.