The recent Ebola epidemic and the resultant flurry of research activity made me wonder about the ethics of blinded placebo trials when the disease is this lethal. Merck’s trial of rVSV-ZEBOV avoided the issue with a novel trial design.
The recent Ebola outbreak resulted in more than 11,000 deaths in West Africa. Of course the concept of the placebo is one of the key elements of drug trials enshrined under GCP rules, but in a disease that claims the lives of over one-third of sufferers, is it ethical to randomly give participants a treatment you know to be inert?
In testing its rVSV-ZEBOV vaccine, Merck used a ring vaccination approach – in which a “ring” of 7,651 individuals deemed at greatest risk of exposure were treated to try and prevent spread. There was no actual placebo. Instead participants were split into two groups – those who received the vaccine immediately upon exposure and those who rec4eived it after a delay.
In an interim analysis published in The Lancet, every patient who received the vaccine directly after Ebola broke out in his or her village was virus-free within 6 to 10 days, suggesting rVSV-ZEBOV could be highly effective at stemming the spread of Ebola. Even the delayed vaccination group only showed 16 cases of Ebola.
The study is still ongoing, but the randomization period is over and all patients from here on will receive immediate doses of the vaccine. The investigators are also still assessing its safety, noting that there have been just 43 adverse events in the Phase III study so far.
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