Oral cholera vaccine proves efficacy

Copyright: WHO

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  • Oral vaccine shows 45 per cent preventive efficacy in Bangladesh trials
  • Vaccine works best with steps like hand-washing and using safe drinking water
  • Shanchol, the vaccine, is recommended for stockpiling in endemic areas

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[NEW DELHI] An oral cholera vaccine (OCV) developed in India can drastically reduce the incidence of the food and water-borne diarrhoeal disease, say researchers who showed its effectiveness in five-year-long trials in Bangladesh.

Results of the first real-life trials of the OCV, called Shanchol, published this month in The Lancet (9 July), showed 45 per cent preventive efficacy when combined with simple interventions like hand-washing and access to safe drinking water. The study, funded by the Bill and Melinda Gates Foundation, was carried out in Dhaka.

Firdausi Qadri, director of the vaccines centre at the International Centre for Diarrhoeal Disease and Research, Bangladesh, who led the trial, says that the findings “show that a routine oral cholera vaccination programme in cholera-endemic countries could substantially reduce the burden of disease and greatly contribute to cholera control efforts.”

Cholera, caused by the bacterium Vibrio cholerae, results in acute watery stools. Over one billion people are at risk in more than 50 cholera-endemic countries, including Bangladesh which accounts for 300,000 cases and 4,500 deaths every year.

On the basis of a field trial in Kolkata, in 2011, WHO prequalified the use of Shanchol, an oral, killed whole-cell cholera vaccine suitable for low-income, cholera-endemic regions. “The vaccine is cheap, two doses cost US$ 3.70, around a third of the price of the other licensed oral vaccine, Dukoral,” says Qadri.

Shanchol produced by the Indian vaccine giant, Shantha Biotechnics, a part of the global Sanofi group, has been commercially available in India since 2009.

In the Dhaka study, about 270,000 residents from the Mirpur area received Shanchol doses, 14 days apart, in three groups — vaccination alone, vaccination plus  interventions like hand-washing and access to chlorinated drinking water, and a non-intervention group.

Two years after the trial vaccinations, the researchers found Shanchol’s effectiveness to be 37 per cent in the vaccination-only group and 45 per cent in the vaccination-and-intervention group.

Qadri and her colleagues have conducted trials in the rural Bangladesh using the health ministry’s extended programme for immunisation (EPI). “The results suggest that it is feasible to deliver the vaccine using our routine EPI facilities in rural sites,” says Qadri.

To Maureen O’Leary, epidemiology lecturer, London School of Hygiene and Tropical Medicine, the study did not show the effect of Shanchol beyond five years. However, she says that the study provides a realistic estimate on “how best to deploy cholera vaccine in reality”.

According to O’Leary, the study will “aid ministries of health in making decisions about whether to introduce the vaccine, based on local cholera epidemiology and on the cost effectiveness of the vaccine in their country.”

Dominique Legros, cholera expert at the WHO, says the findings help substantiate the significance of maintaining a stockpile of Shanchol and mobilising the vaccine to cholera-endemic regions for preventing and controlling the disease.

This article has been produced by SciDev.Net's South Asia desk.