摘要：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. Healthy People 2010 1 established the objective of full immunization of 80% of the nation’s children aged 2 years and younger. Current vaccination surveillance data demonstrate that additional progress toward this goal is necessary, as only 74% of children aged 19–35 months have received their fourth diphtheria–tetanus–pertussis vaccine (DTP4), third poliovirus vaccine (Polio3), first measles–mumps–rubella (MMR1), third Haemophilus influenzae type b, and third hepatitis B vaccine doses (i.e., the 4:3:1:3:3 vaccination series). 2 Other findings indicate that although most children ultimately complete the 4:3:1 vaccination series, remarkably few children do so by the recommended ages. 3, 4 The barriers to childhood vaccinations are complex and persistent. Findings from previous research indicate that vaccination status can be influenced by a multitude of factors, including population characteristics 5– 13 as well as numerous provider-related factors. 14– 18 Some of the most fundamental barriers to childhood vaccinations collectively fall under inadequate access to health services. Poor access to care is thought to be a strong deterrent to childhood vaccinations; therefore, having health insurance as well as a regular source of care are both of critical importance. 15, 16, 18 There is ample evidence that reducing out-of-pocket costs to families—such as through insurance coverage—is an effective mechanism to increase vaccination rates. 19 However, other research findings indicate that some children may have adequate health insurance yet still have incomplete vaccinations. 13, 20 This may be, in part, a result of the fact that having health insurance does not necessarily guarantee having a regular source of care—and having both is believed to be important. There is evidence indicating that persons not having health insurance and a usual source of medical care are far less likely to have had a physician visit in the previous year, compared with their insured counterparts who have a usual source of care. 21 Having health insurance and a usual source of care has been demonstrated to influence the likelihood of children completing the 4:3:1 vaccination series 22 ; however, the role these factors play in age-appropriate vaccination is not well understood. We hypothesized that having health insurance and a regular source of care each increase the likelihood of age-appropriate vaccination, and having both provides the highest likelihood of a child receiving vaccinations according to the recommended schedule. We evaluated this hypothesis through a simulation in which the likelihood of age-appropriate vaccination was assessed for those with and without health insurance and for those with and without a usual source of medical care. Our analysis is based on a nationally representative sample of children, extending the generalizability of previous research conducted on populations of more limited scope. The importance of assessing childhood vaccination status in age-appropriate terms has been previously demonstrated, 3, 4 and therefore we consider the likelihood of vaccination from 2 perspectives: whether a child is likely to ever receive a vaccine dose (i.e., be up to date) and whether the dose is likely to be received age-appropriately.
