Is a conference paper whose proceedings will be published in IEEE Xplore counted as a publication?
I would be a bit hesitant to include it as a "publication" rather than as "under review". I don't know what field or conference you are referring to, but in CS, my experience is that review happens before the conference (and before acceptance) rather than after. And since in CS, conferences are a main publication venue, it would seem appropriate to include under those circumstances. You seem to be describing something different, however. 

But your words "will be published...after the papers have been reviewed" makes this seem a bit tentative. 

I suggest you wait before you include it as a publication unless you qualify it in some way. You don't need to omit it entirely, just be honest and clear about the actual state of the world when you send it out.