The purpose of this study is to evaluate the safety and immunogenicity of a new formulation of a locally-produced bivalent, (O-1 and O-139) killed whole cell oral cholera vaccine among Vietnamese adults.

Cholera remains to be a serious public health problem worldwide. In the mid-1980s following technology transfer from Sweden, Vietnamese scientists developed and produced an oral killed monovalent cholera vaccine for Vietnam's public health programs. A 2-dose regimen of this vaccine has been shown to be safe and efficacious. Subsequently, a bivalent vaccine was developed containing the newly emergent O139 V. cholerae. This vaccine has several advantages over the existing Swedish vaccine. It confers protection against the El Tor biotype in younger children, is considerably less expensive, does not require a buffer during administration and does not require strict cold chain requirements. However, this vaccine is not licensed for use in countries other than Vietnam. In order to make this vaccine available to other countries, the IVI has provided technical assistance to produce this vaccine following the WHO Good Manufacturing Practices standards. A new formulation of the current oral cholera vaccine was produced following these guidelines. Since this vaccine is slightly different from the previous vaccine, a study is necessary to demonstrate safety and immunogenicity for local licensure and larger Phase III studies in other countries.

Inclusion Criteria:

• Healthy non-pregnant adults
• Available in the study area for 1 month

Exclusion Criteria:

• Diarrhea for the past week
• Antibiotic use in the past week
• Intake of anti-diarrheal medicines in the past week
• One or more episodes of diarrhea or abdominal pain lasting for 2 weeks during the past 6 months
• Abdominal pain, nausea, vomiting, loss of appetite or generalized ill feeling for the past 24 hours
• Pregnancy