Currently there are two licensed inactivated vibrio oral vaccines (Dukoral® [Crucell; Leiden, The Netherlands] and Shanchol™ [Shantha Biotechnics; Hyderabad, India]) that are pre-qualified by the World Health Organization (WHO) for procurement by United Nations (UN) agencies. Each of these vaccines requires a two-dose regimen which is difficult to implement in the face of explosive outbreaks of cholera in unsettled situations in developing countries. For this reason there is great interest in identifying a cholera vaccine that can provide rapid onset of protection following the ingestion of just a single oral dose.