Currently available oral cholera vaccines

To date, three oral cholera vaccines are available, which have been shown to be safe, immunogenic and effective. These vaccines have been licensed in some countries and are mainly used by travellers.

WC/rBS vaccine

One vaccine consists of killed whole-cell V. cholerae O1 with purified recombinant B-subunit of cholera toxoid (WC/rBS). Clinical trials have been performed in Bangladesh, Peru and Sweden. Efficacy trials have shown that this vaccine is safe and confers 85–90% protection during six months in all age groups after administration of two doses, one week apart. In Bangladesh, protection declined rapidly after six months in young children, but was still about 60% in older children and adults after two years.

Variant WC/rBS vaccine

As a result of technology transfer, a variant of the WC/rBS vaccine containing no recombinant B-subunit has been produced and tested in Viet Nam. It is administered in two doses, one week apart. A field trial conducted in 1992–1993 in Viet Nam showed a protective efficacy of 66% at eight months in all age groups. The vaccine is licensed only in Viet Nam.

CVD 103-HgR vaccine

Another vaccine consists of an attenuated live oral genetically modified V. cholerae O1 strain (CVD 103-HgR). Placebo-controlled trials in several countries have demonstrated the safety and immunogenicity of a single dose of CVD 103-HgR. The efficacy of this oral vaccine has been investigated in adult volunteers in the United States of America, where it has been found that a single dose confers high protection (95%) against V. cholerae. Classical and 65% protection against V. cholerae El Tor following a challenge given three months after administration.

A large field trial performed in Indonesia has not shown convincing protection in a population exposed to cholera a long time after immunization. However, a retrospective analysis of a mass-vaccination campaign performed by the Government of Micronesia in 2000 suggests evidence of protective efficacy when the single-dose oral cholera vaccine is used for the control of an ongoing outbreak under field conditions and associated with standard control measures.