Objectives: We examined the associations of having health insurance and having a usual source of medical care with age-appropriate childhood vaccination.
Methods: Simulations were conducted with multivariate logistic regression models and a nationally representative sample of children to assess the likelihood of age-appropriate vaccination.
Results: Simulated provision of health insurance and a usual source of medical care produced substantial increases in the likelihood of doses being received age-appropriately. Increases in the likelihood of a child's being up to date were also observed, but these increases typically were smaller than for age-appropriate vaccination.
Conclusions: Changes in childhood vaccination status should be assessed in age-appropriate terms, because measures of "up to date" status may not capture the effects of immunization interventions.