Cholera vaccine


 * Associate Editors-In-Chief: Priyamvada Singh, MBBS [mailto:psingh@perfuse.org]

Overview
Cholera vaccine is a vaccine used against cholera and traveler's diarrhea.

Vaccine
The first vaccines against cholera were developed in the late nineteenth century. These injected whole cell vaccine became increasingly popular until they were replaced by oral vaccines starting in the 1980s. Although no longer in use, the injected cholera vaccines are effective for people living where cholera is endemic. They offer significant degrees of protection for up to two years after a single shot, and for three to four years with annual booster. They reduce the risk of death from cholera by 50% in the first year after vaccination.

There are two variants of the oral vaccine currently in use: WC-rBS and BivWC. WC-rBS (marketed as "Dukoral") is a monovalent inactivated vaccine containing killed whole cells of V. cholerae O1 plus additional recombinant cholera toxin B subunit. BivWC (marketed as "Shanchol" and "mORCVAX") is a bivalent inactivated vaccine containing killed whole cells of V. cholerae O1 and V. cholerae O139. mORCVAX is only available in Vietnam. These oral vaccines provide protection in 52% of cases the first year following vaccination and in 62% of cases the second year.

Bacterial strains of both Inaba and Ogawa serotypes and of El Tor and Classical biotypes are included in the vaccine. Dukoral is taken orally with bicarbonate buffer, which protects the antigens from the gastric acid. The vaccine acts by inducing antibodies against both the bacterial components and CTB. The antibacterial intestinal antibodies prevent the bacteria from attaching to the intestinal wall thereby impeding colonisation of V. cholerae O1. The anti-toxin intestinal antibodies prevent the cholera toxin from binding to the intestinal mucosal surface thereby preventing the toxin-mediated diarrhoeal symptoms. Dukoral also protects against traveler's diarrhea.

The cholera vaccine is largely used by backpackers and persons visiting locations where there is a high risk of cholera infection. However, since it does not provide 100% immunity from the disease food hygiene precautions should also be taken into consideration when visiting an area where there is a high risk of becoming infected with cholera. Although the protection observed has been described as "moderate", herd immunity can multiply the effectiveness of vaccination. Although the vaccine can be dangerous for children, administration of the vaccine to adults can confer protection to children indirectly.