Rationale: Oral vaccination is known to induce a systemic immune response as well as an immune response in mucosal tissues, and can therefore serve as a model to study systemic and mucosal immunity. In this study, the oral cholera vaccine Dukoral® was chosen as model vaccine. The kinetics of the immune response and the interaction with a raw milk matrix have been evaluated in a previous, pilot study (NL49042.081.14). Based on the outcomes of this pilot, in this study oral cholera vaccination will be applied to study the support of immunity by raw milk, compared to heat-treated milk. The study design has been optimised based on previous results: study duration is extended and sample size is based on relevant change and known variation in the primary outcome parameters.