Enterotoxigenic Escherichia coli (ETEC) are the most common cause of childhood diarrhea in developing countries and are thought to cause about 400,000 deaths annually.

In collaboration with U.S. NAMRU-3 (Cairo), U.S. NIH, University of Gothenburg, SBL Vaccine, and WHO, the IVI collaborated on the first Phase 3 efficacy trial of an ETEC vaccine ever to be conducted in children residing in an area with endemic ETEC diarrhea. The vaccine, developed at the University of Gothenburg and produced by Activ Biotech in Sweden, consists of a mixture of formalinized ETEC whole cells that express the colonization factor antigens that are most epidemiologically prevalent among clinical ETEC isolates from patients in developing countries. The vaccine also contains cholera toxin B subunit, to take advantage of the antigenic similarity between the B subunits of cholera toxin and the heat labile enterotoxin of ETEC. Children 6-12 months were enrolled in the placebo-controlled, randomized trial conducted near Alexandria, Egypt. The code for the trial was broken in April 2002, permitting two complete years of follow-up of all participants. Initial analyses have revealed no statistically significant protection. Further analyses are now being done to explore possible reasons for the unexpected lack of vaccine efficacy.