can be developed depend on many factors, such as the existing scientific knowledge of the agent (or a similar organism), its molecular biology, rate of transmission, pathogenesis, how the human immune system responds to natural infection, and the nature of protective immunity.

Economic factors may also impede vaccine development, because it requires an extensive, up-front investment in research. Most vaccine manufacturers (and policymakers) are reluctant to make the necessary financial commitment since few vaccines are highly profitable and strict federal safety and efficacy requirements make the risk of failure a very real possibility. Vaccine developers must also take into account the extra costs that may arise from liability claims for injuries or deaths blamed on vaccines. This concern has forced a number of vaccine manufacturers out of the marketplace.

Industry might be encouraged to assume a greater role in vaccine development if it was asked to participate in a public/private sector collaboration, similar to NIH's National Cooperative Vaccine Development Groups, whose focus is HIV disease vaccines. Another alternative might be to offer industry various economic incentives, such as minimum guaranteed purchases, to conduct its own development work.

Given the various disincentives to vaccine development for more common pathogens, the development of vaccines for emerging microbes is even more problematic. There may be potentially catastrophic consequences if the development process is left entirely to free enterprise. The committee thus believes that a comprehensive strategy is urgently needed. To bring a new vaccine rapidly from the research laboratory into general use—a necessary criterion if one hopes to prevent or control an emerging infectious disease—will require an integrated national process that

• defines the need for a vaccine, its technical requirements, target populations, and delivery systems;

• ensures the purchase and use of the developed product through purchase guarantees and targeted immunization programs;

• relies as much as possible on the capability of private industry to manage the vaccine development process, through the use of contracted production, if necessary;

• utilizes the capacity of the NIAID to manage and support basic, applied, clinical, and field research, and of the CDC and academia to conduct field evaluations and develop implementation programs;

• is centrally coordinated to take maximum advantage of the capabilities of the public and private sectors; and

• is prepared for the possible rapid emergence of novel disease threats, such as occurred in the 1918-1919 influenza pandemic.

The committee recommends that the United States develop a means for generating stockpiles of selected vaccines and a "surge" capacity for vaccine