The first arm includes subjects, who were immunized with two Shanchol™ doses, five years prior. In this study, arm one will receive one Shanchol™ booster dose at baseline and one booster dose on day fourteen.

The second arm includes subjects, who received two placebo doses, five years prior. Arm two will receive a primary immunization series consisting of one Shanchol™ dose at baseline and one at day fourteen

The third arm includes subjects, who received two placebo doses, five years prior. This third arm will not receive any intervention and will serve to represent a baseline immune response by vaccine naïve individuals exposed to natural exposure.

This killed, whole cell, bivalent vaccine will be presented as a creamish white suspension. Upon storage, a white sediment and clear supernatant may be observed. The recommended dose (1.5ml) of the vaccine must be administered orally. The primary vaccination schedule consists of two doses given at an interval of two weeks. After vigorous shaking of the vial, 1.5 ml should be poured into the mouth of the recipient, followed by water ad libitum. The vaccine can alternatively be administered with a disposable syringe (without needle) after removing the contents from the vial and squirted into the mouth of the recipient.

Vaccine is administered in 1.5 mL vials by mouth in 2 doses, given 2 weeks apart. The vaccine appears as a creamy white suspension.

To determine whether two doses of Shanchol™ administered to a previously immunized cohort elicits similar immune responses (greater than fourfold rise in serum vibriocidal antibody titers through IgM) to those achieved by a primary immunization series in an unimmunized cohort stratified by age (6-14 and ≥15 years old),

To determine if a one dose booster regimen of Shanchol™ administered to a previously immunized cohort can elicit similar immune responses (through serum IgM) to those achieved by primary immunization in an unimmunized cohort stratified by age (6-14 and ≥15 years old)