IMMUNIZATION COVERAGE AMONG INFANTS ENROLLED IN THE TENNESSEE MEDICAID PROGRAM

Objectives: To determine immunization coverage of infants receiving Me dicaid in Tennessee and to identify risk factors for failure to comple te recommended vaccinations by 24 months of age. Design: Retrospective cohort study. Subjects: A total of 33615 children born in one of thre e urban Tennessee counties from 1980 through 1989 who were enrolled in Medicaid throughout their first 24 months of life. Main Outcome Measu res: Receipt of four diphtheria-tetanus-pertussis, three oral polio, a nd one measles-mumps-rubella vaccines by 24 months of age (up-to-date) , as recorded in computerized county immunization records and Medicaid billing files. Results: Overall, 45% of infants enrolled in Medicaid in the three urban counties completed the recommended vaccinations by 24 months. The proportion of infants up-to-date peaked at 50% for thos e born in 1982 and 1983, and decreased to 44% for those born in 1989. The only strong independent predictors of immunization completion were number of prior births for the mother, timing of the first immunizati on, and county of birth. The proportion up-to-date tvas 56% for first- born children compared with 27% for those whose mothers had at least t hree prior births; 55% for those whose first immunization was on time compared with 22% for those with a delay in the first immunization; an d 63%, 52%, and 37% for infants born in the three respective counties. Maternal age, education, race, and marital status predicted immunizat ion completeness only weakly or not at all. Conclusion: Of infants bor n in the three counties in the 1980s who were enrolled in the Tennesse e Medicaid program, fewer than half completed their recommended childh ood-vaccinations by 24 months of age. The large differences in immuniz ation levels between infants enrolled in the Medicaid program in the t hree counties, not accounted for by differences in demographics, sugge st that factors related to the health care and vaccine delivery system have important effects on achieving adequate immunization of these in fants.