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Second, a small amount of disease occurs at an early age, before completed immunization schedules can confer full protection. Taking into account these two factors, the proportion of illness that is vaccine preventable with a subunit vaccine is estimated to be about 60 percent.

In the case of a genetically attenuated strain, engineering a strain to carry a sufficient number of antigens to cover all strains might be difficult, so a somewhat lower proportion of the total disease burden is assumed to be potentially vaccine preventable (i.e., about 50 percent).

Efficacy (as predicted in Chapter 5, Table 5.1) in both cases is estimated against challenge by strains in the vaccine. In both cases the vaccine is assured to confer long-lasting immunity.


Diarrhea due to enterotoxigenic E. coli would be suitable for vaccine control if relatively long-lasting protection could be elicited at an early age to carry children throughout the early childhood period when they are at greatest risk of dehydration and death. The prevalence of this and other diarrheal diseases in areas of developing countries where medical care services are rarely available suggests that a prevention approach is desirable.

Alternative Control Measures and Treatments

Death from acute diarrhea most often results from dehydration caused by unreplaced losses of body water and electrolytes. The treatment of diarrhea due to enterotoxigenic E. coli depends primarily on replacement of these deficits. The increased use of oral rehydration therapy (ORT) could have a considerable impact on the disease burden, especially deaths. However, the application of ORT depends on the availability of oral rehydration salt preparations and community education programs explaining how to use them. A scenario assuming increased ORT application is included in the calculations described in Chapter 7, based on the estimates in Table D-2.2 and discussed in Appendix C.

Adjunctive therapy with antibiotics also may reduce the duration and volume of diarrhea. Co-trimoxazole is the only drug that has been evaluated, and it has been studied mainly in adults with experimentally induced diarrhea or with travelers’ diarrhea.

Transmission of enterotoxigenic E. coli is thought to be primarily by water and food. Presumably, the disease could be prevented by avoidance of fecally contaminated water and attention to hygienic food handling techniques. The provision of clean water and improved sanitation in developing countries is desirable on many grounds but is unlikely to be a rapid solution to diarrhea prevention.

In addition, for travelers, prophylactic antibiotics have been utilized and appear to prevent enterotoxigenic E. coli diarrhea. However, because of the risks involved in taking antibiotics, chemo-

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