The future of the National Immunization Survey

Abstract

In the recent report of the Institute of Medicine entitled, Calling the Shots: Immunization Finance and Policies,1 the U.S. immunization system was described as a national treasure. In our view, the National Immunization Survey (NIS) is clearly one of the jewels in that treasure. Since its beginning in 1994, the NIS has helped us keep a finger on the pulse of the immunization system. A model public health evaluation tool, it provides essential and timely information that has been used to improve immunization programs around the nation. At the same time, the NIS has served as a kind of laboratory allowing us to improve our monitoring methods. The survey’s timeliness and flexibility ensure a bright future for this premier evaluation tool of the nation’s immunization system. Since 1994, the NIS has been the source of a very important set of numbers: immunization coverage levels among children aged 19 to 35 months at the national and state levels, and for selected urban areas.2 Foremost among the benefits of this nationwide survey is that it allows comparisons between states and selected urban areas. Previously, areaor state-specific coverage estimates were rarely comparable, because different survey methods were employed. This ability to compare has resulted in informal competition among immunization programs, and has provided positive motivation. The progress achieved since 1994 in immunization coverage at the national level is remarkable, but this success must be repeated every year in every community nationwide, because nearly 11,000 babies are born in the United States every day, or about 4 million every year. The NIS has provided important data on risk factors for undervaccination, such as family income below the poverty level, maternal age ,19 years, and more than five household occupants. NIS findings are used to target technical assistance to areas with high proportions of children at risk for underimmunization. The NIS helps us keep abreast of important changes in the nation’s immunization delivery system, which further enables us to target our research and programmatic efforts. For example, the NIS provides information on the growing proportion of children who receive immunizations from private providers. In 1999, a total of 62% of children living in suburban areas, 52% in urban areas, and 41% in rural areas received all their vaccines from private providers.3 Based on these data and earlier NIS information, we have emphasized research and programmatic interventions in quality assurance for private-sector immunization settings, and we have directed even more effort into strengthening partnerships with private-provider organizations. Eliminating racial disparities is a major component of Healthy People 2010 objectives,4 and the NIS will continue to allow us to monitor progress in this endeavor. The sampling frame of the NIS is large enough to measure immunization coverage for the major racial and ethnic groups in the nation. The NIS has documented improvements in vaccination coverage by race and ethnicity; by 1997, most racial and ethnic groups reached the 90% goal for individual vaccines, but work remains.5 As reported in the NIS,2 the gap in coverage in 1999 for the 4:3:1:3 series (consisting of at least four doses of diphtheria and tetanus toxoids and pertussis vaccine; three doses of poliovirus vaccine; one dose of measles, mumps, and rubella vaccine; and three doses of the Haemophilus influenzae type b vaccine) between African-American and white children is 7.2% (73.8%62.6% vs 81.0%61.0%, respectively). The NIS serves as an early warning system that can alert us to declines in immunization coverage. Should coverage begin to decline, timely actions can be taken before the drop escalates enough to result in an epidemic. The NIS updates reports of vaccination coverage at the national level and for states and urban areas twice a year, 6 months after the data-collection period is completed. Taking preventive action based on coverage data is preferable to learning about an epidemic from disease surveillance. By the time an epidemic is identified by disease surveillance systems, it is often too late to make much difference in its outcome. The 1989–1991 measles epidemic illustrated that monitoring disease and immunization coverage of kindergarten and first-grade children only was not adequate to prevent outbreaks in younger children. The NIS is designed to focus on this preschool population, the group at greatest risk of complications from most vaccine-preventable diseases. The NIS has offered the opportunity to implement lessons learned from earlier national surveys of vacciFrom the National Immunization Program, Centers for Disease Control and Prevention, Atlanta, Georgia Address correspondence to: Jose F. Cordero, MD, 1600 Clifton Road, Mailstop E-05, Atlanta, GA 30333. E-mail: Jcordero@cdc.gov. Address reprint requests to: National Immunization Program Resource Center, Centers for Disease Control and Prevention, 1600 Clifton Road NE, Mailstop E-34, Atlanta, GA 30333. Fax: (404) 639-8828.