It's some 450 years old
Scientists from the University of Florence, in Italy, claimed to have found some of the earliest human remains to have given birth to the myth of vampires. The skeleton, found in a mass grave near Venice, had a brick in its mouth, so as to prevent the dead from chewing on its shroud or veil, and to suck the blood of others. All the victims that were found in the pit were killed by the plague, which people back in the 16th century believed was carried by the mythical creatures, and not by fleas and personal hygiene, or lack thereof.
In official and private documents, dating back to those dark times, the “vampires” were widely mentioned, as people believed that they fed on the dead. The modern adaptation of the myth has nothing to do with what people back in the day believed. They didn't hold that the creatures sucked blood out of the body via the neck, but that they spread diseases, for instance the bubonic plague. They termed vampire any corpse that would chew its own shroud.
Forensic experts say that it's perfectly normal for some of the dead to spill blood through the mouth, an effect that often tears the funeral veil, and forces it into the mouth of the deceased. When people back in the 15th or 16th centuries saw that, they usually got very scared, hence the myth of supernatural creatures roaming the night. As a basic method of counteracting the “actions of the vampires,” grave diggers had the habit of placing bricks into the mouths of those they deemed “suspicious.”
University of Florence investigator Matteo Borrini was behind the new find, which was made at Lazzaretto Nuovo Island, in Venice. Despite the fact that he claimed his discovery to be of the first ever vampire, Wichita State University researcher Peer Moore-Jansen argues that he already unearthed similar remains in Poland in the past, and that the claims are “a little ridiculous.” Borrini defends himself by saying that the grave and the content he found represent the first tangible “exorcism evidence against vampires.”