It makes them extremely dangerous, and they should not be sought out or approached by anyone who is not a qualified exorcist. However, we have found physical forms within catacombs and mausoleums. The vampire traditionally sleeps in its tomb by day, issuing as a living form only at night. Vampires are biocidal. They destroy all living forms.
Vampires exist outside of time.
Time does not apply to one until it is exorcised. There is an element of truth, as evil, once invited, will enter - whether a vampire or some other form of evil. There is no population as such. Vampires may be found anywhere on the face of the earth. Though some regions have been known to suffer vampire epidemics.