• knowledge of clinical signs and symptoms of the disease to allow differentiation from similar syndromes

• identification of the pathogen and its major characteristics, including the existence of strains and serotypes, their infectivity, their virulence, their antigenicity, and the nature of essential immunogens

• the existence of specific techniques for cultivation of the pathogen

• identification of non-human models of infection

• knowledge of the human immune response to the pathogen, including the duration and type of response (e.g., serum antibody, mucosal antibody, or cell-mediated immunity)

• definition of the target population.

All aspects of the knowledge base that involve technical feasibility must be reassessed frequently: a vaccine not foreseeable today may become reality because of one unexpected development in the laboratory. This is especially true in the fields relevant for vaccine development, because the capacity of modern biotechnology has only begun to be explored.

The criteria for selection of candidates for accelerated vaccine development do not address the general question of which vaccines are most needed in the United States. For some diseases that impose major burdens on the U.S. population, the knowledge base is not sufficient to allow consideration for accelerated vaccine development by NIAID. Nevertheless, portions of the analysis described in this report can be applied to these disease problems to gain useful information about long-term goals and potential benefits. The description of disease burden considerations in Chapter 4 and the discussion of utilization patterns in Chapter 6 may be especially helpful in this regard.

The committee hopes that the selection of candidates for accelerated vaccine development will not divert funds from long-term basic research programs. For these programs, the scientific merit of the research proposal should continue to be the dominant criterion for funding.

During the tenure of this committee, research has led to rapid generation of new knowledge about the suspected etiology of Acquired Immune Deficiency Syndrome (AIDS). The committee decided, however, that speculation in this report regarding the future availability and efficacy of an AIDS vaccine would not be useful.