time, determining the immunization status of individuals and groups has become more difficult, especially among vulnerable populations. The complexity of the immunization schedule is likely to contribute to more missed opportunities that could decrease coverage levels and reduce the benefits of vaccines.
In addition to the challenges resulting from scientific advances and changes in the environment, the national immunization effort must adapt to the increasing complexity of the financing, service delivery, and public health information systems. Many vulnerable populations now receive vaccines from private health care providers, as the well-insured have long done. Yet the public sector still has primary responsibility for financing vaccine purchases and surveillance efforts for at-risk groups. A patchwork of public and private programs and funding streams that is inadequately described and poorly understood has complicated the national effort to supply, deliver, and monitor immunizations.
The public sector currently relies on a combination of Vaccines for Children (VFC), Section 317, and state funds to purchase childhood vaccines. These programs for vaccine purchase are described in Chapter 3. VFC now provides vaccine for approximately 35 percent of the national birth cohort (National Vaccine Advisory Committee [NVAC], 1999a). In 1998, VFC purchased approximately 37 million doses of vaccine, while Section 317 funds were used to purchase about 13 million doses (information provided by CDC). States also use their own funds to buy vaccine. The states purchased a total of approximately 7 million doses through federal purchase contracts in 1998, and purchased an undetermined number of additional doses directly. Altogether, public-sector funds were used to purchase more than 57 million doses of childhood vaccine in 1998. More than half of all vaccine doses purchased in the United States in 1998 (52.4 percent) were publicly purchased through federal contracts (information provided by CDC).
Although the public sector purchases the majority of vaccine doses, it is not the primary source of vaccine delivery. Historically, virtually all immunizations received by public program beneficiaries were administered in the public sector. With the inception of VFC in 1994 and the rapid growth