I am wondering if Ebola is similar to chickenpox in that the virus never really goes away 100%. If it lingers and the person is still at risk for a reoccurring infection, then Ebola is a lot more dangerous than initially thought. It may require mass vaccinations to provide any long term society resistance.
For biological reasons, Ebola cannot "hide" in the body the way chickenpox does. Chickenpox is a DNA virus, and it can either hide by becoming part of a chromosome or by disguising itself as a chromosome. Ebola cannot do that since it is an RNA virus.
Ebola virus survives in areas of the body that the immune system cannot reach--for instance, in the eye fluid, in breast milk and seminal fluid (where they are stored in glands). Since the immune system cannot reach into those fluid-filled pockets, it cannot kill the virus there. As for the virus, those biological fluids preserve it for prolonged periods since they act as buffers.