The primary aim of this project is to determine changes in the vibriocidal geometric mean titers (GMT) in subjects who receive the second dose of oral cholera vaccine (OCV) at different intervals: 2 weeks, 6 months, or 11 months following the first dose of vaccine. Secondary aims include a) vibriocidal antibody response rates in subjects who receive OCV at 2 weeks, 6 months, or 11 months following the first dose of vaccine, b) age specific serum vibriocidal GMTs following the second dose among participants given the second dose of OCV at intervals of 2 weeks, 6 months, or 11 months following the first dose of vaccine, c) GMT and antibody response rates of Immunoglobulin A (IgA) and Immunoglobulin G (IgG) anti-lipopolysaccharide (LPS) as measured by ELISA following the second dose among participants given the second dose of OCV at intervals of 2 weeks, 6 months, or 11 months following the first dose of vaccine. The hypothesis is that the vibriocidal GMT following the second dose, when given after 6 or 12 months will not be inferior to the response when the second dose is given according to the standard interval of two weeks.

This is an open label, randomized, phase 2 clinical trial of the immunogenicity of killed oral cholera vaccine (OCV) when the vaccine is administered to participants of three age cohorts (1-4 years, 5-14 years, and >14 years) and in three dose interval groups (DIGs). The subjects in each age cohort will be randomized to a DIG of 2 weeks (DIG-1), 6 months (DIG-2) or 11 months (DIG-3). A total of 180 subjects from Douala, Cameroon will be enrolled and these are equally divided between the different groups (20 per age/dose interval group). The OCV to be used in the trial is Shanchol.

Blood samples will be collected before the first dose and at intervals following the first dose depending on the dosing interval group assigned. The serum (or plasma) will be tested for antibodies to cholera.

Inclusion Criteria:

1. Age ≥1 year, stratified into different age groups
2. Living in the Soboum Health Area or adjoining area
3. Good health condition, without clinically significant medical history (by participant or guardian, in case of minor)
4. Not pregnant for female subjects.
5. Available to participate for the study duration, including all planned follow-up visits for up to 18 months from screening.
6. Signed informed consent -

Exclusion Criteria:

1. Presence of a significant medical or psychiatric condition (Examples include: Diagnosis and treatment of tuberculosis (TB) or HIV; renal insufficiency; hepatic disease; oral or parenteral medication known to affect the immune function , such as corticosteroids, other immunosuppressant drugs; or behavioural or memory issues)
2. Ever having received oral cholera vaccine.
3. Receipt of an investigational product (within 30 days before vaccination).
4. History of diarrhoea in 7 days prior to first dose of vaccine (defined as ≥3 unformed loose stools in 24 hours).
5. History of chronic diarrhea (lasting for more than 2 weeks in the past 6 months)
6. Current use of laxatives, antacids, or other agents to lower stomach acidity?
7. Planning to become pregnant in the next 2 years

We will publish the results of this study in a peer reviewed publication and will make the data available on request after the paper has been published.

When the manuscript is published.

Researchers will need to submit a request to the investigators detailing their plans for analysis.