The Telegraph adds this:
The succession of plagues which ravaged Europe between 1300 and 1700 fostered the belief in vampires, mainly because the decomposition of corpses was not well understood, Mr Borrini said.
Gravediggers reopening mass graves would sometimes come across bodies bloated by gas, with hair still growing, and blood seeping from their mouths and believe them to be still alive.
The shrouds used to cover the faces of the dead were often decayed by bacteria in the mouth, revealing the corpse’s teeth, and vampires became known as “shroud-eaters”.
According to medieval medical and religious texts, the “undead” were believed to spread pestilence in order to suck the remaining life from corpses until they acquired the strength to return to the streets again.
"To kill the vampire you had to remove the shroud from its mouth, which was its food like the milk of a child, and put something uneatable in there," said Borrini. "It’s possible that other corpses have been found with bricks in their mouths, but this is the first time the ritual has been recognised."
I’m no expert on human anatomy but it looks like her jaw was broken to fit it in …