Efficacy of an Enterotoxigenic

The efficacy of an Oral Whole Cell ETEC Vaccine (OEV) against Travelers' Diarrhea (TD) was reexamined using novel outcome and immunologic measures. More specifically, a recently developed disease severity score and alternative clinical endpoints were evaluated as part of an initial validation effort to access the efficacy of a vaccine intervention for the first time in travelers to an ETEC endemic area. A randomized, double-blind, placebo-controlled trial followed travelers to Guatemala or Mexico up to 28 days after arrival in the country following vaccination (two doses two weeks apart) with an ETEC vaccine. Fecal samples were collected upon arrival, departure, and during TD for pathogen identification. Serum was collected in a subset of subjects to determine IgA cholera toxin B subunit (CTB) antibody titers upon their arrival in the country. The ETEC vaccine's efficacy, utilizing a TD severity score and other alternative endpoints, including the relationship between antibody levels and TD risk, was assessed and compared to the per-protocol primary efficacy endpoint. A total of 1435 subjects completed 7-28 days of follow-up and had available data. Vaccine efficacy was higher against more severe (≥5 unformed stools/24 h) ETEC-attributable TD and when accounting for immunologic take (PE ≥ 50%;