The Complicated World of Ebola Vaccine Trials
The frustration, at times approaching despair, has been evident for years when talk among filovirus scientists turned to Ebola vaccines. In high-containment biosafety level 4 (BSL-4) laboratories, several vaccines have saved animals from what should have been lethal doses of the virus. Mice, guinea pigs and nonhuman primates—the best stand-ins for man—have been protected. A few of these experimental vaccines even progressed to the tantalizing point where they were injected into humans, in first-in-man trials in the U.S. But there the research always stalled.
All that is changing. Ebola vaccines are finally getting their shot.
Starting as early as January clinical trials designed to test two leading experimental Ebola vaccines will start to enroll volunteers in Liberia. Trials in Sierra Leone and Guinea will follow. With the rate of new infections dropping in Liberia, time is of the essence if the goal of proving whether the vaccines protect people is to be met.
No one involved in the Ebola response wants to see more cases. But the reality of vaccine research is that you can only find out if these experimental preparations work in settings where the targeted pathogen is spreading. If infection rates drop too low, the planned Liberian trial—slated to enroll 27,000 people—would have to be expanded, adding to the cost, complexity and the time it will take to get to the answers.