Immunogenicity of One Versus Two Doses of Killed Oral Cholera Vaccine

Cholera is an important public health problem worldwide, particularly in endemic areas of the developing world. In 2004, 101 383 cholera cases and 2345 deaths were reported to the WHO. Provision of safe water and food, adequate sanitation and improved personal and community hygiene are the main public health interventions against cholera. These measures cannot be implemented in the near future in the most cholera-endemic areas.

Phase II trials of this reformulated killed oral cholera vaccine were performed in SonLa, Vietnam and Kolkata, India. Significant vibriocidal antibody responses were observed among vaccine recipients.

Distribution of 2 doses of the cholera vaccine is often difficult in field settings and limits its utility in emergency situations, since an interval of 2 weeks is usually required between doses. Recent data from Vietnam suggests that greater vibriocidal responses following 2 doses are elicited compared to previous formulations. Furthermore, in a study in Bangladesh comparing immune responses to the vaccine among children supplemented with vitamin A and zinc, seroconversion after the first dose was robust in all groups suggesting that one dose may be used in the control of cholera.

Data regarding the immune response following one dose of this reformulated vaccine is currently unavailable. If a single dose of this vaccine is confirmed to be immunogenic to recipients, then this vaccine may be used more extensively for public health purposes, especially during times of outbreaks.

The objective of this study is to confirm the safety of the killed oral cholera vaccine among adult and children volunteers.

Inclusion criteria

• Healthy adult male and non-pregnant female adults aged 18-40 years and healthy children aged 1-17 years

All subjects must satisfy the following criteria at study entry:

• Male or female adult residents aged 18-40 years or children aged 1- 17 years who the investigator believes will comply with the requirements of the protocol (i.e. available for follow-up visits and specimen collection)
• For females of reproductive age, they must not be pregnant (as determined by verbal screening)
• Written informed consent obtained from subjects or their guardians, and written assent for children aged 12-17 years.
• Healthy subjects as determined by: medical history, physical examination, clinical judgement of the investigator.

Exclusion criteria

• Ongoing serious chronic disease
• Immunocompromising condition or therapy
• Diarrhea (3 or more loose stools within a 24-hour period) 6 weeks prior to enrollment
• one or two episodes of diarrhea lasting for more than 2 weeks in the past 6 months
• one or two episodes of abdominal pain lasting for more than 2 weeks in the past 6 months
• intake of any anti-diarrhoeal medicine in the past week
• abdominal pain or cramps, loss of appetite, nausea, general ill-feeling or vomiting in the past 24 hours
• acute disease one week prior to enrollment, with or without fever. Temperature > or = 38 degrees C (oral) or axillary temperature > or = 37.5 degrees C warrants deferral of the vaccination pending recovery of the subject
• receipt of antibiotics in past 14 days
• receipt of live or killed enteric vaccine in last month
• receipt of killed oral cholear vaccine