Recognizing that the assessment and documentation of immunization status are complicated by the movements of individuals, health care providers, and health finance systems, several states, local communities, and private health plans have initiated electronic registries to monitor immunization rates within a community or health plan. Immunization registries are “confidential, computerized information systems that contain information about immunizations and children” (National Vaccine Advisory Committee [NVAC], 1999b:2). They have also been described as “automated systems that manage immunization information” (Horne et al., forthcoming:3) and as “a computerized database that gathers immunization information on all children (with preschool children commonly a high priority) in a population defined by a specific geographic area, health maintenance organization (HMO), enrollment, etc.” (Wood et al., 1999:233).6
Most efforts to develop immunization registries in this country have focused on infants and preschool children. Some managed care companies and HMOs, however, have developed and maintain information systems that they use to monitor their effectiveness and efficiency in providing both childhood and adult immunizations to their enrolled populations.
Registry development began in 1974 when Delaware created VacAttack, a community-based registry built to collect childhood immunization data from all pediatric and family practice providers in the state (Ortega et al., 1997). In the 1980s, several large HMOs started to develop immunization registries (Wood et al., 1999). For example, Group Health Cooperative of Puget Sound created a computer-based data record for all immunizations administered to its 350,000 enrollees in the late 1980s. HMOs continued to build registries in the 1990s. In 1991, CDC collaborated with several large West Coast HMOs in the Vaccine Safety Datalink project, which established both immunization registries and systems for tracking adverse reaction events (Davis et al., 1997; Wood et al., 1999).
In 1991, the Robert Wood Johnson Foundation (RWJF) launched the All Kids Count national childhood immunization registry initiative in response to both the measles outbreak of the late 1980s and the low immunization rates of preschool children in the United States (Watson et al., 1997). These computerized information systems were designed to perform three functions: (1) to provide a computerized database for use by providers in monitoring the immunization status of individual children; (2) to identify children due or overdue for immunizations and notify their parents/guardians of the need to obtain vaccinations; and (3) to provide information for use in identifying underserved populations, targeting resources to these pockets of need, and evaluating outreach program efforts. Between 1992 and 1997, RWJF collaborated with five other private