Safety and immunogenicity of an oral, killed enterotoxigenic Escherichia coli-cholera toxin B subunit vaccine in Egyptian adults

Enterotoxigenic Escherichia coli (ETEC) is the leading cause of bacterial diarrhea in young children in developing countries. The safety and immunogenicity of a killed, oral ETEC vaccine consisting of whole cells plus recombinantly produced cholera toxin B subunit (rCTB) was evaluated in Egypt, which is endemic for ETEC diarrhea. Seventy-four healthy Egyptian adults (21- 45 years old) were randomized and received two doses of the ETEC/rCTB vaccine (E003) or placebo 2 weeks apart. The frequency of adverse events after either dose did not differ by treatment group, and no severe adverse events were reported. After vaccination, peripheral blood IgA B cell responses to CTB (100%) and to vaccine colonization factor antigens CFA/I (94%), CS4 (100%), CS2 (81%), and CS1 (69%) were significantly higher than response rates for the placebo group. These favorable results in Egyptian adults indicate that the ETEC/rCTB vaccine is a promising candidate for evaluation in younger age groups in this setting.