production technology to developing countries, most likely under the guidance and assistance of such international agencies as the WHO.
To develop a theoretical basis for predicting vaccine utilization in the United States, the committee adapted basic concepts of the “health belief model” (HBM), a social-psychological model of health-related decision making developed by U.S. Public Health Service psychologists in the early 1950s (Becker, 1974; Janz and Becker, 1984). Questions exist concerning the validity of the HBM as a predictive tool, but it offers an appropriate conceptual framework for studying public immunization behavior within a defined, relatively homogeneous population. A brief review of the health belief model and a description of the methods used by the committee to predict vaccine utilization in the United States appear in Volume I of the committee’s report (Institute of Medicine, 1985a).
To estimate probable utilization, each vaccine candidate was assigned scores to reflect lay (target population) and provider perceptions of risk of illness, severity of disease, vaccine benefits, and barriers to vaccination. These scores were then combined into overall vaccine acceptance scores for each candidate. The combined scores were used to estimate vaccine utilization in situations in which individuals could freely choose their health behavior, and in which other factors, for example, the efficiency of the health care system, did not otherwise limit utilization. (Mandatory immunization requirements, e.g., for school admission, if enforced, tend to override the influence of these other factors in determining acceptance.)
Little research has been conducted to determine whether the health belief model as formulated for the U.S. population is applicable to other societies. Several studies of voluntary vaccine utilization in developing countries suggest that the factors determining relevant health decisions in the developing world are similar to those postulated in the HBM (Adeniyi, 1972; Azurin and Alvero, 1971; Hingson, 1974; Hingson and Lin, 1972; Hsu, 1955; Lin et al., 1971; Ogionowo, 1973; Ristori, 1969). It is important to recognize, however, that local perceptions of disease and health care are molded by social, educational, and economic conditions radically different from those in the United States. Accurate assessment of these perceptions requires input from individuals familiar with the cultures involved.
The committee believes that its general approach to estimate U.S. vaccine utilization probably could be adapted to any defined population, for example, a specific country, where the range of HBM perceptions can be estimated with reasonable confidence.