Cholera is an acute diarrhoeal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae. It has a short incubation period of few hours to 5 days. Once infected, the patient develops watery diarrhoea which can lead to severe dehydration and death if treatment is not promptly given. Left untreated, mortality from severe dehydration approaches 50%. However, with timely treatment of dehydration with oral rehydration solution, mortality can be reduced below 1%. Cholera remains endemic in many parts of the world especially in Asia and Africa where access to safe drinking water and basic sanitation is inadequate.

Available Cholera Vaccines Industry

There are currently two licensed oral cholera vaccines recommended by WHO for use – Dukoral and Shanchol. Dukoral is a whole cell, killed vaccine containing the inactivated V. cholerae O1 and O139 strains along with the recombinant B subunit of cholera toxin. It provides 85% protection for 6 months after two doses administered at least 1 week apart. Shanchol is a bivalent vaccine containing killed whole cell V. cholerae O1 strains of both Inaba and Ogawa serotypes. It has demonstrated an efficacy of around 66% for 1 year after a single dose. Both vaccines have been prequalified by WHO for purchase by UN agencies after meeting stringent standards of quality, safety and efficacy.

Cholera Vaccines Industry Control Strategies

Cholera Vaccines are recommended by WHO to be used in conjunction with other preventive measures like water, sanitation and hygiene interventions especially in endemic and epidemic prone areas. They are useful in preventing initial infections as well as decreasing transmission by serving as a firewall between ongoing transmission and susceptible populations. Vaccination provides direct protection at individual level as well as contributes to herd immunity by limiting circulation of the bacterium in communities. Some key contexts where vaccines have shown effective impact are:

- Reactive vaccination campaigns during outbreaks help contain the spread by ring vaccination of contacts and target populations. This was successfully implemented in Haiti outbreak in 2010-2011.

- Preventive vaccination campaigns in endemic areas with seasonal peaks. Repeated annual or biannual vaccination has substantially reduced cases in Bangladesh, India and other places.

- Vaccination of displaced populations in camps or settlements. This was demonstrated to significantly reduce attacks in refugee camps in northern Uganda.

- Mass vaccination campaigns before seasonal peak. Vaccinating a critical proportion of the population 1-3 months before the rainy season appears to flatten the seasonal curve.

While vaccines alone are insufficient, integration with other interventions has demonstrated synergy and additive effect. Combining vaccination with improvements in water and sanitation leads to sustained control and ultimately elimination of cholera from communities.