health departments (New York City, Detroit, San Diego, and rural Colorado) have participated in a Community Health Network demonstration study to determine whether collaboration with academic health centers or managed care organizations would influence and improve vaccination coverage within the entire population in the designated region (A.Bauer, CDC, personal communication, May 21, 1999).
As noted above, immunization coverage studies within small geographic areas or among specific populations (including low-income workers, Medicaid or Medicare participants who are served by managed care organizations, public housing residents, and migrant farmworkers) can provide important data on variations in coverage patterns that require attention through state and national health finance and health care policies and practices. Local immunization surveys provide intelligence needed to manage the community health system effectively, target needy groups, and ensure accountability within the public and private health care sectors. However, significant barriers challenge such efforts to track vulnerable groups:
Surveys of baseline coverage for Medicaid populations, including the coverage rates for families served by managed care organizations, are not consistently available, nor can results be compared across survey designs.
The difficulty of gaining routine access to households of very poor families, due in part to the high rates of mobility among such families, poses significant methodological barriers to data collection efforts.
Special population studies are commonly funded for limited periods of time through research or state grant awards supported directly by CDC. These special area studies are inconsistent and often difficult to compare because they use different standards of coverage, different age groups, and different survey methods.
CASA Surveys. CASA is CDC-developed software and associated procedures for assessing coverage levels for a clinic or practice. The sample for 2-year-olds consists of children aged 24 to 35 months; coverage is calculated at the 24-month mark. Charts for children are included in the sample if there is a record of at least one medical or immunization visit; a chart can be excluded from the sample under certain stringent conditions.3 Providers sometimes complain that the inclusion criteria are overly broad.4 They report that parents often fail to notify their provider when they move, and when this happens, the chart does not bear a “moved or gone elsewhere” notation. Further, providers in birthing hospitals say patients may come to the hospital’s outpatient clinic for the first or second