To evaluate the preventive impact, demand, acceptability, uptake, feasibility, and cost-effectiveness of a two-dose regimen of the OCV Shanchol in children living in urban slums in Bangladesh, Investigators will conduct a targeted mass immunization programme, using an innovative approach successfully deployed by the Bangladesh government in its recent countrywide campaign of MR vaccination of 52 million children aged 9 months to 14 years (<15 years). Investigators will undertake a census of a geographic population of approximately 300,000 persons, with GIS locations of each household. This census will be updated every 6 months during the follow-up period to permit tracking of births, deaths, and migrations, including changes in location of each individual's residence. Following the initial census, the OCV will be offered to all non-pregnant individuals aged 1 to 14 years. Operational research and economic studies will evaluate the coverage, feasibility, acceptability, demand, costs and cost-effectiveness of this vaccination programme.

Burden: Cholera remains a major global problem, resulting in more than 100,000 deaths and several million cases annually , mostly children. Vaccination has been reconsidered as a key component of the public health response to cholera. Bangladesh has one of the world's highest burdens of endemic cholera, with an estimated 300,000 cholera cases and over 4,500 deaths annually, and with high caseloads and frequent outbreaks in more than half of the country. The endemicity of cholera in Bangladesh is demonstrated by the predictable yearly occurrence of the disease in the country's high-risk districts and the repetitive seasonal pattern of cholera outbreaks, either in spring or autumn, or both .

Knowledge gap: More evidence is needed to address uncertainties around the cholera disease burden, as well as the impact, feasibility, and cost-effectiveness of various vaccination strategies against cholera, to add to the existing knowledge base. A special need for acquiring field evidence of these vaccine attributes in settings with endemic cholera, which account for a very large fraction of the global cholera disease burden, is also recognized .

Relevance: Nonetheless, the assertion that selective vaccination of children with OCV is an impactful approach to controlling cholera at the population level rests on unproven assumptions, since there are no studies that directly address this vaccination strategy. Therefore, further study on whether targeted mass immunization can create efficiencies that general mass immunization would not, is warranted. The Investigators therefore believe that the most compelling question for the control of endemic cholera in Bangladesh is how targeting 1-14 year olds in urban slums, using the established platform of targeted mass childhood immunization recently deployed by the GOB for measles-rubella (MR) vaccine, impacts on the overall burden of cholera in the population and how feasible and cost-effective this strategy is. Addressing these questions will add to the evidence base on the most cost efficient and effective settings and strategies for use of OCV to control endemic disease and optimize health impact.

Hypothesis : Vaccination of children under 15 years of age in urban slums of Dhaka will confer at least 50% overall protection to the entire population through combined direct and indirect protective effects and it will be cost effective.

Objectives:To evaluate the feasibility, efficiency, and impact of a two-dose regimen of the oral cholera vaccine (OCV) Shanchol delivered to children aged 1-14 years residing in urban slums, leveraging a targeted mass immunization delivery platform used for other vaccines in Bangladesh.

Methods: Observational design based on the contrast of persons who do and do not get vaccinated according to public health practice(Age-targeted mass immunization program).

Inclusion Criteria:

• All healthy, consenting, non-pregnant (as ascertained by history) residents of a high risk group, 1 to 14 years of age, of the study area will be included in the study.

Exclusion Criteria:

• Aged less than 1 year and more than 14 years
• History of intake of any cholera vaccine
• Pregnant women (identified through verbal screening)

The study population will be recruited from different wards of Dhaka city corporation (wards 42, 43, 45, 46, 47, 48, 58, 91 and 92 which are now numbered as 29,30,32,33,34 of Dhaka North City Corporation and 14,22,55,56,57 of Dhaka South City Corporation respectively).

Individual participant data will not be shared to anybody.