Single dose of oral cholera vaccine proves protective in an endemic setting
SEOUL, May 11, 2016- A new study by the International Vaccine Institute (IVI) and icddr,b and published in The New England Journal of Medicine 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 be eagerly 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 study, done in collaboration with the Government of Bangladesh, and funded by the Bill & Melinda Gates Foundation, was conducted in the urban slums of Mirpur, an area of Dhaka, Bangladesh with high rates of cholera. 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% protective against all cholera episodes up to 6 months after dosing and 63% 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, says that “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. Our results are very encouraging and show that a single dose of the OCV is effective in preventing disease in older children and adults in a highly cholera endemic setting in the world.
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 has potential 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 Professor John D. Clemens, Executive Director of icddr,b.
Previously, the two-dose regimen of Shanchol, a World Health Organization (WHO) pre-qualified oral cholera vaccine, was found in a trial in Kolkata to confer 65% protection that was sustained for at least 5 years. More recently, when delivered through routine government services in Dhaka, the same regimen was found by icddr,b scientists to confer 53% protection over two years of follow-up, as recently published in The Lancet.
The findings further support use of the vaccine against epidemic and endemic cholera. The oral cholera vaccine was developed through international product development partnerships led by IVI with partners from Vietnam, India, Sweden, South Korea and the United States. More recently, Euvichol was prequalified by WHO and is the first oral cholera vaccine made in South Korea for global public health.
“The potential public health impact is significant,” said Dr. Jerome Kim, Director General of IVI, “A single dose OCV will help increase access of the vaccine in humanitarian crises and other settings with very challenging conditions that makes vaccine delivery difficult.”
The full findings of the single-dose study were published in the New England Journal of Medicine.
The International Vaccine Institute (IVI) is the world’s only international organization devoted exclusively to developing and introducing new and improved vaccines to protect the world’s poorest people, especially children in developing countries. Established in 1997, IVI operates as an independent international organization under a treaty signed by 35 countries and the World Health Organization. The Institute conducts research in more than 20 countries of Asia, Africa and Latin America on vaccines against enteric and diarrheal infections, Japanese encephalitis, MERS, and dengue fever, and develops new and improved vaccines at its headquarters in Seoul, Republic of Korea. For more information, please visit www.ivi.int