Traditional Bram Stoker vampires are less possible than Nessie. It isn't physically possible. I posted a long drawn out comment explaining all of the medical reasons why a human can't become a vampire before. It simply isn't possible. Another species, aliens yeah. Maybe they could. But a human digestive system would have to be totall reconstructed and an average male vamp would have to drain 18 humans dry per day to live. Not to mention the 100s of other medical reasons they can't exist. But I think if 500 people were disappearing or dying in an area in a month then it would be newsworthy.

I believe more in Psychic Vampires as opposed to the body needing other's blood to survive(beyond blood transfusions). Sure they can exist if subculture wise(and I'm not talking about Twilight kids!) you practice blood letting/drinking(minus true Porphyria). On a more Lamia as an example, demonic note, maybe. But less so as Porphyria, as reports are not conclusive. Though we just may not know...