if it has a vinyl coating it will be difficult to paint over. not aware of any primers specifically for this. some wallpapers are designed to be wiped clean and therefore repellant, paint will not take to it very well.
better to try to strip it - you will probably find that its one of those papers that is designed so that the when stripped the surface comes away readily and easily and often in a single piece (on each drop) leaving its backing paper on the wall. this is so that the wallpaper backing becomes the lining paper for the new paper. you should be able to paint straight on top of this.