topsie, the report of natural immunity comes from research by IRD, a French institute specializing in overseas research.
The report is not new (2010). To see a translated summary, Google "337- Possible natural immunity to Ebola?"

It is suspected that they might have come in contact with the virus through saliva of fruit bats on their fruits. Bats are suspected of being the natural reservoir of the virus.
Labs in several countries are working towards a vaccine. How much this will be helped if at all by the high percentage (15%) of Gabonese with immunity, I don't know.

Emory University hospitals (Atlanta) is one research institution leading vaccine study. See http://news.edu/stories/2102/12/ebola_virus_protein_decoy/index.html (or Google "Ebola virus uses protein decoy to subvert the host immune response."