Cholera, a rapidly dehydrating diarrheal disease, is caused by ingestion of Vibrio cholerae, serogroup O1 or O139. The World Health Organization (WHO) estimates that 1.4 billion people were at risk for cholera in 2012. More than 90% of reported cases occur in Africa, and most of the remainder occur in southern Asia. In 2010, only 10 months after it was hit by a major earthquake, Haiti experienced the most severe cholera epidemic of the past century, with 699,579 cases and 8539 related deaths reported as of February 11, 2014. This was the first time cholera had been documented in Haiti, despite the occurrence of devastating outbreaks in the Caribbean in the 19th century and in Latin America between 1991 and 2001 (see map). Cholera is a disease of poverty, linked to poor sanitation and a lack of potable water. Establishment of an adequate sanitation and potable-water system is the most definitive way to prevent and limit its spread. However, the cost of instituting adequate sanitation systems, one of the United Nations Millennium Development Goals, is prohibitive for the countries that are affected by cholera: it would cost an estimated $2.2 billion, for example, to adequately improve access to water and sanitation in Haiti. Water, sanitation, and hygiene (WASH) practices are the cornerstones of cholera prevention and control. The promotion of WASH practices, the creation of rehydration centers, use of antibiotics, and training of health personnel during the first months of the Haitian epidemic led to a dramatic reduction in cholera associated mortality, from 4% to 1.5%.2 Yet a survey in the slums of Port-au-Prince showed that although people were aware of hand-washing methods, they did not have soap and water to implement them. What role should oral cholera vaccine (OCV) play, in combination with WASH practices, in epidemic conditions?