stimulate the appropriate use of vaccines once they are developed—is all the more necessary.

The cooperation and synergistic activities of the public and private sectors have led to remarkable successes. The development of the acellular pertussis vaccines is one such example. NIAID invested significant funds to support clinical trials of acellular pertussis vaccines, which are now licensed and recommended for use. Tensions, however, are inevitable and probably healthy. For example, the committee is aware of tensions between the needs of FDA for mechanisms that it believes are necessary for ensuring the safety and efficacy of the vaccines and the effect that some of these mechanisms have on the financial requirements for licensure. Examples of these discussed by the committee include the financial burdens of pilot production and the high costs of the complex clinical trials required by FDA to demonstrate efficacy as well as safety. Although the committee did not study in detail the relationship between public and private research on vaccines, it is clear that improvements can be made to foster collaboration when market forces cannot guarantee that a for-profit vaccine manufacturer will risk an investment in the development and manufacture of a particular vaccine or a particular type of vaccines.

The private companies involved in vaccine research, development, and manufacturing expect and are entitled to a reasonable return on their investments. In fact, market forces have led to the development of many vaccines, such as the Haemophilus influenzae type b (Hib) vaccine. The burden of disease caused by Hib infection was significant, the target population (the annual birth cohort of approximately 4 million infants) had regular contact with the medical community, vaccinations were already an integral part of health care for this population, and a guaranteed market was confidently predicted. The Hib vaccine was, in fact, recommended for routine use by major advisory bodies such as the Advisory Committee on Immunization Practices of CDC and the Red Book Committee of the American Academy of Pediatrics, and immunization with the Hib vaccine was required for entrance into most day-care centers.

In an ideal world, every vaccine of medical or public health importance would be developed. It is not clear that 20 years prior to licensure of polio vaccines either the disease burden or the basic science knowledge required for vaccine development would have been sufficient for inclusion in a modeling exercise such as the one undertaken for this report. However, it most certainly would have been a compelling candidate for analysis by 3 to 7 years prior to licensure, owing to the increase in paralytic disease and to advances in tissue culture and virology. This underscores the need for a dynamic research program that is not limited to the candidate vaccines discussed in this report and for the dynamic use of a model for ongoing evaluation of R&D priorities.