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Cholera

Vaccine

A vaccine consisting of killed whole-cell V. cholerae O1 in combination with a recombinant B-subunit of cholera toxin (WC/rBS) has been marketed since the early 1990s. This killed vaccine is well tolerated and confers high-level (85–90%) protection for 6 months after the second immunization in all vaccinees aged more than 2 years. The level of protection is still about 50%, 3 years after immunization in vaccinees who were aged over 5 years at the time of vaccination. Primary immunization consists of two oral doses 7–14 days apart for adults and children aged 6 years and over. For children aged 2–5 years, three doses are recommended. Intake of food and drinks should be avoided 1 hour before and after vaccination. If the second dose is delayed for more than 6 weeks, vaccination should be restarted. Following primary immunization, protection against cholera may be expected after about 1 week. Booster doses are recommended after 2 years for adults and children aged 6 years and over, and every 6 months for children aged 2–5 years. The vaccine is not licensed for individuals under 2 years of age.

In studies of travellers to countries or areas reporting cholera outbreaks, WC/rBS was also found to induce approximately 50% short-term protection against diarrhoea caused by enterotoxigenic Escherichia coli (ETEC).

Two closely related bivalent oral cholera vaccines are available in India and Viet Nam. These killed whole-cell vaccines are based on V. cholerae serogroups O1 and O139 and do not contain the toxin B-subunit; they are reported to be safe and efficacious, providing 66–67% protection for at least two years against clinically significant cholera in countries or areas reporting outbreaks. The Indian vaccine is intended for both the national and the international market.