Diarrhoeal diseases are a major source of preventable morbidity and mortality, and in 2015 claimed the lives of more than 1·3 million people, of whom 499 000 were children younger than 5 years.As a contributor to the global burden of diarrhoeal disease, Vibrio cholera is a particularly harsh pathogen, causing rapid onset of severe nausea, vomiting, and profuse watery diarrhoea that can lead to death within hours—even of the healthiest young adults
A single-dose regimen of inactivated whole-cell oral cholera vaccine (OCV) is attractive because it reduces logistical challenges for vaccination and could enable more people to be vaccinated. Efficacy of a single dose of an OCV vaccine during the 6 months following dosing has been reported previously. Dr.Firdausi Qadri and associates have conducted a placebo-controlled, double-blind randomised Trial at Dhaka and found that a single dose provided protection for at least 2 years when given to adults (vaccine protective efficacy against all cholera episodes 59%, 95% CI 42–71) and to children aged 5 years or older (52%, 8–75).The study has been published in The Lancet Infectious Diseases.
In the study individuals aged 1 year or older with no history of receipt of OCV were randomly assigned to receive a single dose of inactivated OCV or oral placebo.The primary endpoint was a confirmed episode of non-bloody diarrhoea for which the onset was at least 7 days after dosing and a faecal culture was positive for Vibrio cholera O1 or O139. The researchers assessed the protective efficacy of the OCV against culture-confirmed cholera occurring 7–730 days after dosing with both crude and multivariable per-protocol analyses.
The researchers found that a single dose of the inactivated whole-cell OCV offered protection to older children and adults that was sustained for at least 2 years. The absence of protection of young children might reflect a lesser degree of pre-existing natural immunity in this age group. Further studies are needed to determine how best to protect the youngest individuals, and to identify the ideal dosing schedule of the vaccine.
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