Development of a safe, effective Ebola vaccine is an important goal for bringing the current epidemic under control and minimizing future outbreaks. Before a vaccine can be given to at-risk populations, however, it must be tested to determine whether it is safe and assess the level of protection it provides. Ebola vaccine trials are currently underway in Guinea and Liberia, two of the three hardest-hit countries in the ongoing Ebola epidemic, and the US Centers for Disease Control and Prevention (CDC) will soon be starting a vaccine trial in Sierra Leone.
The Ebola epidemic has been declining in Sierra Leone and the rate of decline varies in different regions. A team of researchers led by Steve Bellan at The University of Texas at Austin, and including University of Florida researchers Juliet Pulliam and Carl Pearson, has analyzed potential designs for the Sierra Leone trial, taking into account recent trends in Ebola case numbers. They have found that the trial CDC had originally planned in Sierra Leone – a so-called ‘stepped-wedge’ design – would be unlikely to be informative, with a 6 months study leaving researchers uncertain as to whether the vaccine was effective. In contrast, a trial similar to the design that CDC announced on April 15 is much more likely to be able to detect an effective vaccine. This work also emphasizes that any trial implemented in Sierra Leone needs to begin as soon as possible, as the informative power of any trial is decreasing substantially as the epidemic continues to decline. You can read the article here.