Immune Response to a Delayed Second Dose of Oral Cholera Vaccine

Inclusion Criteria: * Any healthy individual ≥ 1 year-old and younger than 40 years old , eligible for OCV vaccination (not suffering from a medical condition that contraindicates vaccination, i.e. any acute illness, including acute gastrointestinal illness or acute febrile illness). * Living in the study area with no plan to move away over the study period (up to 18 months). * Who provided written informed consent or whose representative (mother, father or main caretaker) provided written informed consent in case of individuals younger than 18 years. A written assent will also be obtained from adolescents (10-17 years) * An individual who (or whose mother, father or main caretaker) is, based on the judgment of the investigator, capable of complying with the study requirements. Exclusion Criteria: * Known history of hypersensitivity reactions to other vaccines. * Individual acutely ill or with signs of infection at the time of enrolment (e.g. fever \> 38⁰C) * Gastrointestinal symptoms including nausea, vomiting, diarrhea, or decreased appetite within 24 hours prior to study initiation . * Diarrhea, administration of antidiarrheal drugs or antibiotics to treat diarrhea or abdominal pain either lasting 2 weeks or longer within 6 months prior to study initiation, or occurring during the week before study initiation. * Other vaccination within 1 week prior to study initiation or planned vaccination during the following month after vaccine intake . * Participation in another trial with investigational product within 1 month prior to study initiation. * Pregnant (as determined by a urine test on the day of each vaccination) or lactating women, women of reproductive age planning pregnancy before the end of the study period (up to minimum 18 months). * An individual thought to have difficulty participating in the study due to other reasons (such as mental disorders, alcohol or drug intoxication), based on the judgment of the investigator. * History of cholera vaccination or history of cholera as diagnosed by a medical person in a health facility (with or without laboratory confirmation). * Severe chronic diseases or medical conditions, based on the medical judgment of the investigator, such as known low hemoglobin level or symptomatic anemia, severe acute malnutrition, chronic infection (e.g. tuberculosis), sequel of poliomyelitis, immunodeficiency due to symptomatic HIV/AIDS. * Based on participant verbal reporting of the participant at inclusion, more than two persons in households \<5 persons or three participants in households ≥ 5 persons. * Thrombocytopenia or bleeding disorders or other known contraindication to venipuncture. Severe medical condition that contraindicates vaccination. In particular, a) known history of immune function disorders; or b) current use of steroids cytotoxic drugs, immunosuppressant, immune modifying drug, Prednisolone, Azathioprine, Cyclosporin, Interferon, G-CSF, Tacrolimus, Everolimus, Sirolimus; or c) known active malignancy with the exception of adequately treated basal cell or squamous cell skin cancer, in situ cervical cancer, adequately treated Stage I cancer from which the patient is currently in complete remission, or any other cancer from which the patient has been disease-free for 5 years; or d) known uncompensated NYHA Class 3 or 4 congestive heart failure; or e) known myocardial infarction within the previous 6 months; or f) known neurological and/or psychiatric disorder.