on or improve the immunization status of clients who visit their offices only once.

At present, little compelling evidence has emerged that managed care plans do any better or worse than fee-for-service systems in improving the immunization status of their members (Fairbrother et al., 1996). More important, variations in measurement and the movement of covered populations make it difficult to compare plan performance in improving immunization rates. The exclusion of providers that serve predominantly low-income clients or hard-to-reach groups from enrollment or assessment measures can contribute to positive measures of immunization coverage that suggest good performance. Such exclusionary practices are difficult to detect, especially in the absence of small-area population-based assessments that have sufficient sensitivity to reveal disparities in coverage rates and service utilization patterns among vulnerable groups. The lack of national or state-level trend data for Medicaid and other disadvantaged populations within private health plans (whether capitated managed care organizations or fee-for-service) also makes it difficult to follow immunization coverage rates within high-risk groups. States and local communities thus rely on special population-based studies to monitor coverage rates and to determine whether private plans within their areas are providing immunizations as expected (see Box 5–1). These special studies are generally financed by state public health agencies or CDC; both types of studies are commonly supported by the Section 317 program.

Inconsistencies in the measurement of immunization status within high-risk populations inhibit efforts to monitor community health, as well as the impact of private health plans on client and community outcomes. The absence of reliable data confounds attempts to hold plans accountable for the quality of their performance in improving the health status of their most vulnerable participants.

Several factors make it difficult to monitor service-delivery patterns within the private sector:

  • Large numbers of uninsured and Medicaid families shift between public health clinics and private health plans (often as a result of monthly eligibility determinations), and the scattering of immunization records becomes a significant problem in establishing accountability requirements within multiple health plans. In California, for example, 40 percent of children lose Medicaid each year (Kuttner, 1999; Fairbrother, 2000; Fairbrother, 1999).

  • Most health plans do not provide separate reimbursements to service providers for immunizations that are included in capitation payments for primary care or well-baby services for infants and children.

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