The leading Ebola vaccine candidate has been left undeveloped for a decade and a half.

Following initial trials, scientists are now urgently working to determine whether a vaccine created in 2011 can effectively combat the current Bundibugyo outbreak in Congo.

A new vaccine successfully protected three macaques from the deadly Bundibugyo Ebola strain, which caused severe symptoms like fever and bleeding in unvaccinated monkeys. While the vaccinated group remained healthy, the virus ultimately proved fatal to two-thirds of the unvaccinated animals.

There is still a chance the vaccine may not work. Because of limited resources in the DRC and the difficulties of shipping refrigerated blood samples to the United States, researchers have not yet been able to obtain a live sample of the Bundibugyo virus to test. While the current strain is thought to be 98 percent identical to earlier versions, that 2 percent difference means the vaccine might not be as effective this time around.

Still, Geisbert is hopeful. He points out that the genetic sequences are close enough that he does not expect any problems, though he admits there are no guarantees. The International AIDS Vaccine Initiative in New York will now step in to manufacture the vaccine, taking on a global health project that offers little financial reward for commercial drug companies.