The Ebola Virus Disease (EVD) outbreak in West Africa is by far the largest ever recorded. A safe and effective vaccine against Ebola virus disease (EVD) may help end the ongoing epidemic in West Africa and control future outbreaks. A variety of candidates are currently being evaluated in Phase I, II and III trials.
During this presentation, we describe a novel trial design that we refer to as a ring vaccination trial since it adopts the outbreak containment strategy of ring vaccination. In a ring vaccination trial, a patient newly diagnosed with EVD becomes the index case around whom a socially and geographically defined ring of his or her contacts and the contacts of these contacts is formed. This ring is then randomized to either immediate or deferred vaccination with the candidate vaccine.
As the ring can also be viewed as a cluster and because randomisation occurs at the level of the ring, the extensive literature on the design, analysis and reporting of cluster randomized trials can be readily adopted. We illustrate the approach by summarizing the protocol and results of a ring vaccination trial against EVD in Guinea, West Africa. This strategy may increase trial power, reduce the required sample size, and simplify trial logistics as compared to standard vaccine trial designs and can be useful for performing vaccine trials during outbreaks.
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