ETEC EPIDEMIOLOGY AND VACCINE RESEARCH IN LOWER EGYPT

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Enterotoxigenic Escherichia coli (ETEC) diarrhea is hyperendemic among young Egyptian children, with a balanced distribution of toxin phenotypes from pathogenic isolates. These features make it logical to develop a field site for the evaluation of ETEC epidemiology and ETEC vaccines in Egypt. We are engaged in a collaborative program of research in lower Egypt designed to characterize ETEC diarrhea in a pediatric cohort and to test the safety and immunogenicity of a promising killed oral ETEC vaccine candidate in preparation for a field trial of vaccine efficacy. We have followed a cohort of children under 3 years with twice-weekly active surveillance in Abu Homos (Beheira governorate) to determine the age-specific incidence rate of ETEC diarrhea, by toxin and colonization factor (CFA) phenotypes. During 18 months of follow-up of 288 children in Abu Homos, ETEC was isoalted in 290 (24%) of the 1232 detected diarrheal episodes; the incidence rates of ETEC (episodes per child-year) were 1.5, 1.6, and 0.8 in the first, second, and third years of life. Concurrent with establishment of this surveillance, we conducted randomized, placebo-controlled Phase 2 studies of killed oral ETEC vaccine, administered as a two-dose regimen to 76 adults, 107 children aged 6-12 years, and and 106 children aged 2-5 years in Benha, near Cairo. Each of these studies demonstrated the vaccine to be well-tolerated and to induce significant musosal immune responses to vaccine antigens. A similarly designed trial of the vaccine, administered to infants will be launched during the coming months.