I must admit that I never saw it as a vampire movie, either. Monster movie, sure, but not vampires. That would have made it better, IMHO (remember that I actually like the movie). The book alluded to vampires and then changed courses, so basically the movie being a "vampire movie" just means that it never followed through and changed course like the novel.
The most merciful thing in the world, I think, is the inability of the human mind to correlate all its contents. ... The piecing together of dissociated knowledge will open up such terrifying vistas of reality, and of our frightful position therein, that we shall either go mad from the revelation or flee from the light into the peace and safety of a new dark age.
~ Howard Phillips Lovecraft