There is actually a vaccine for one of the more common strains of ebola virus. But the current outbreak is a much newer and much less common strain (first recorded in 2007) that doesn't have any vaccines yet. The first step (happening now) is research to see if the existing vaccine has any effectiveness against this strain - doesn't look great so far but there is also barely any research completed yet. In general, creating vaccines is not only expensive and slow but also involves some measure of luck, and has a lot of variance depending on the nature of any given virus. So it's always rasier said than done.