The U.S. achievement in reducing the burden of infectious disease and increasing immunization coverage rates throughout the states has been accomplished through a series of incremental initiatives over the past 50 years (see Appendix B). An ongoing partnership between the public and private health sectors has emerged that includes extensive collaboration among federal, state, and local health agencies. The result is a dynamic and flexible immunization system that has adapted to evolving science and new vaccines; changing social conditions; and shifting health care finance patterns within all settings, from remote rural counties to metropolitan areas.
In contrast with many other industrialized nations, the United States has a health care system that is highly decentralized and depends primarily on the private sector to deliver services. Each regional health care system is shaped by local circumstances, resources, and needs, as well as by national goals and policies. Though cumbersome, this system has demonstrated an extraordinary capacity to ensure the reliable delivery of an increasing number of vaccine antigens in a growing number of private and public health care settings for an expanding range of age groups, including newborns, preschool and school-aged children, adolescents, and adults.
At present, however, federal and state roles within the national immunization partnership are unstable. Several trends contribute to this instability: rapid acceleration in the science of vaccine research and production, systemic changes in the health care environment of the United States (especially the emergence of managed care organizations), and shifts in thinking within the Congress about the roles and responsibilities of federal and state health agencies in building and supporting public health services. The instability is worrisome because it can create pressure points and blind spots that can swiftly contribute to outbreaks of infectious disease, as was seen in the 1989–1991 measles epidemic in the United States that contributed to 43,000 cases and resulted in more than 100 deaths, particularly among children below age 5 (see Box 1–3) (NVAC, 1991).
The persistence of low immunization coverage rates for routine vaccines (especially measles, rubella, diphtheria, and pertussis) within metropolitan areas is cause for serious concern. Constant vigilance is required to protect the gains that have been made, and to prevent gaps that could result from the addition of new or improved vaccines to the recommended schedules, as well as from changes in health care services for underimmunized populations of adults and children. Unprotected sectors can unexpectedly become sources of infectious disease outbreaks and can