The burdens of illness shown in Tables C.8, C.9, and C.10 are those thought to occur with the present level of intervention. The committee examined how these burdens might be altered by increased application of currently available therapeutic intervention. Among the interventions considered to be of potential major impact were general access to health care and, particularly, the use of oral rehydration therapy (ORT). The committee felt that by the time vaccines became available, the burden of diarrheal illness from enterotoxigenic E. coli and rotavirus might be reduced by increased use of ORT.
To assess the effect of therapeutic intervention on the vaccine candidate priority rankings, the committee calculated the potential health benefits of vaccines for enterotoxigenic E. coli. and rotavirus under two assumptions. The first assumption did not change the current level of intervention. The second one increased ORT (and general access to health care) and resulted in a reduction of deaths from these diseases by 50 percent of current levels. The disease burdens assuming increased ORT use are shown in Tables C.11 (enterotoxigenic E. coli) and C.12 (rotavirus).
For shigellosis, the committee believed that ORT would not have major influence on the disease consequences but that increased use of antibiotics could potentially reduce the mortality resulting from this disease. Realizing this benefit may be impeded by the increasing prevalence of antibiotic-resistant strains of shigella; the consequent need for accurate diagnosis/resistance testing, which may not be available; and in some cases, the need for more expensive antibiotics, which may not be affordable to developing countries. If desired, the effect of wider antibiotic use on the shigellosis disease burden and the ultimate rankings of vaccine benefits can be tested in a manner similar to that used for E. coli and rotavirus.
The committee and subgroups had much discussion on the interaction of diseases causing mortality, and whether or how to quantitatively incorporate these interactions into the calculation of potential vaccine benefits. A notable example is the enhanced mortality among children with diarrhea and measles.
Few attempts have been made to evaluate quantitatively this type of interaction (e.g., Feachem and Koblinsky, 1983). The committee developed a questionnaire to evaluate possible second-order effects of reducing diseases, including the “replacement” of one cause of mortality by another.
For diarrheal diseases, the committee judged that the available data, in general, were not precise and could not suggest the possible effects of disease interactions on a vaccine’s potential health benefit. The capacity of all diarrheal disease to debilitate patients and enhance