An educational model is presented that stresses the importance of the interaction between individual characteristics and intentional educational influences on outcome variation. This model is exemplified by an interventional study of patients with insulin-dependent diabetes mellitus who, despite long-term conventional medical treatment, had been unable to achieve satisfactory hemoglobin Aic levels. Treatment modes and their importance for understanding variations in outcomes are discussed from the interactional perspective suggested in the model.

The approach of providing passive protection to young infants by immunizing pregnant women can bypass the problems of immunological immaturity in the neonate, avoid or delay active immunization of the infant in the first year of life, and prevent transmission of an infection from the mother to the neonate. Optimal vaccines for this approach should induce high immunoglobulin G antibody titers that quickly reach their maximum level after immunization and persist at protective levels for several years, thus providing passive protection in subsequent pregnancies. Specific applications of this approach include the worldwide practice of maternal immunization with tetanus toxoid vaccine and ongoing studies of maternal immunization to prevent Haemophilus influenzae type b, group B strepto-coccal, pneumococcal, meningococcal, and human immunodeficiency virus infection in the infant. Addressing the cultural, sociological, and legal aspects of maternal immunization will be required to ensure the success of this approach.

The generation of diversity of T and B cells begins early in gestation. Selective restrictions in expression of V genes occur in fetal life, but insufficient clonal diversity is not likely to limit newborn immune capabilities. The functional immaturity of neonatal T and B cells is beginning to be defined. Virgin T cells lack the capacity to produce diverse lymphokines, whereas neonatal B cells are less responsive to the lymphokines that promote terminal differentiation to plasma cells.

Molecular biology and, in particular, knowledge of the immune response at the molecular level provide the research community with the opportunity to design vaccines that will elicit the appropriate responses for many diseases. The critical issue is to identify the immune response that correlates with protection. It is remarkable how well the empirical approach has worked; it is essential, therefore, not to ignore the lessons to be learned from these successes. It is particularly essential that each disease and the immune response that affords protection be studied individually so that the appropriate responses can be induced.

The principle that infants can be protected from invasive diseases caused by encapsulated organisms has been proved with the introduction of Haemophilus influenzae type b conjugate vaccines. The use of glycoconjugates to implement some of the goals of the Children's Vaccine Initiative requires a clear delineation of the chemical and immunological specifications for optimal vaccines.

Technologies that promise to enhance the stability of vaccines are likely to be determined by the product-specific physical structure and biological functions of the specific vaccine immunogens. Research may define the extent to which the stability of oral poliovirus vaccine may be improved by the addition of certain antiviral components that bind to the poliovirus capsid or by the application of novel drying technologies.