diseases may overwhelm available medical services and engender particular concern in the at-risk populations.

• The potential for synergistic interaction with other diseases: the committee evaluated the possibility of incorporating into the disease burden estimates of the effects of known synergism, such as between diarrheal disease and measles. The committee concluded that current knowledge of these phenomena did not permit reliable quantification of their consequences, but that they should be recognized in the ultimate selection of priorities.

Problems in obtaining accurate estimates of disease incidence and difficulties in deciding which IME perspectives to adopt also limit the usefulness of the system. Nevertheless, the system has the potential to be a useful tool for selecting priorities for accelerated vaccine development. Recommendations that might remedy some of the problems are made below.

The system described in this chapter allows quantitative comparison of the morbidity and mortality caused by various diseases. It takes into account specific information about each disease (number of cases, complications, sequelae, deaths) and can accommodate various perspectives on the undesirability of various disease consequences.

To illustrate use of the proposed system, diseases that are candidates for accelerated vaccine development have been ranked according to a median of trade-off perspectives elicited from public health experts in developing countries. The effects of adopting alternative perspectives are also discussed. Considerable uncertainty surrounds some of the estimates of disease burdens because data of the desired reliability are not available.

No attempt has been made to calculate the costs of treating diseases in the developing world as a whole because of the many uncertainties involved in such aggregate estimates. However, the committee believes that estimates of total direct costs for certain diseases could be used to help set vaccine priorities in specific countries or regions of the developing world.

The capacity to make rational choices of vaccine development priorities and vaccine formulation would be enhanced by better information on disease incidence and the pathogen serotypes prevalent in particular regions. Therefore, the National Institute of Allergy and Infectious Diseases and other national and international agencies should consider ways to improve the epidemiologic information on infectious diseases.