Robert Pattinson & Kristen Stewart have both claimed that vampires are a myth, and they way they are portrayed in Hollywood, is laughable, however they are quite happy to appear in Vampire Movies, and earn Millions, wouldn't you given the chance.
Psychological studies over a long period of time have shown that the idea of Vampirism, comes from people who in some cases are sectioned under the mental health act, looking pale and weak and completely drained of energy.
There are people trained in occult practices, who can drain the energy from your body while you are in their presence leaving the victim pale and weak just the same as you would look if you had the blood sucked from your body.
If you think that's nonsense consider this have you ever been in a room where when someone entered there is a bad atmosphere. It could be caused by people who have had a dispute each producing negative thoughts, or it could be someone evil who is causing a change to the environment.