Immunization coverage among infants enrolled in the Tennessee Medicaid program
M. R. Griffin, J. Daugherty, G. W. Reed, S. M. Standaert, S. S. Hutchins, R. H. Hutcheson and W. Schaffner
Department of Preventive Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA.
OBJECTIVES: To determine immunization coverage of infants receiving
Medicaid in Tennessee and to identify risk factors for failure to complete
recommended vaccinations by 24 months of age. DESIGN: Retrospective cohort
study. SUBJECTS: A total of 33,615 children born in one of three urban
Tennessee counties from 1980 through 1989 who were enrolled in Medicaid
throughout their first 24 months of life. MAIN OUTCOME MEASURES: Receipt of
four diphtheria-tetanus-pertussis, three oral polio, and 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 those 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 immunization, and county of
birth. The proportion up-to-date was 56% for first-born children compared
with 27% for those whose mothers had at least three prior births; 55% for
those whose first immunization was on time compared with 22% for those with
a delay in the first immunization; and 63%, 52%, and 37% for infants born
in the three respective counties. Maternal age, education, race, and
marital status predicted immunization completeness only weakly or not at
all. CONCLUSIONS: Of infants born in the three counties in the 1980s who
were enrolled in the Tennessee Medicaid program, fewer than half completed
their recommended childhood vaccinations by 24 months of age. The large
differences in immunization levels between infants enrolled in the Medicaid
program in the three counties, not accounted for by differences in
demographics, suggest that factors related to the health care and vaccine
delivery system have important effects on achieving adequate immunization
of these infants.
