UNB, Dhaka :A new study by icddr,b scientists has shown for the first time that a single dose of the oral cholera vaccine Shanchol is effective in older children and adults in an area where cholera is endemic.These findings will eagerly be received globally by health agencies interested in using the vaccine in a single dose in endemic areas where cholera is common, as well as in epidemic situations where disruption of healthcare infrastructure makes it difficult to complete the currently recommended two-dose regimen.The icddr,b study, done in collaboration with the Government of Bangladesh and the International Vaccine Institute in Seoul, and funded by the Bill and Melinda Gates Foundation, was conducted in the urban slums of Mirpur of the city, an area with high rates of cholera. The study report was published in the New England Journal of Medicine. The researchers randomised non-pregnant residents over the age of 1 year to a single dose of oral cholera vaccine (Shanchol) or placebo. The vaccine was 40 percent protective against all cholera episodes up to 6 months after dosing and 63 percent protective against severely dehydrating cholera.Overall, 204,700 received one complete dose of vaccine or placebo and among these 101 first cholera episodes were detected during the six months of follow-up, 37 with severe dehydration. The vaccine was safe and adverse event rates were similar in the vaccine and placebo groups. Dr Firdausi Qadri, a scientist in the Infectious Diseases Division at icddr,b who led the study, said, “A single dose of the oral cholera vaccine was safe and provided protection against cholera for at least 6 months of follow-up.” The vaccine was particularly effective at preventing cholera with severe dehydration. “However, the single dose vaccine was not protective for young children under the age of 5 years although 2 doses of the vaccine has been shown to be effective in this age group,” she noted. At the same time, because the findings show that even a single dose provides at least short-term protection of older children and adults, the vaccine is still likely to be beneficial during epidemics occurring in the wake of humanitarian disasters. “Infrastructural challenges to completing a two-dose regimen should not deter the use of the vaccine to help contain epidemics in these settings,” says Prof John D Clemens, Executive Director of icddr,b and senior author on the paper.
