The Ultimate Vampire Resource and Directory

"The theologian Philip Rohr's gave expression to this popular belief, in 1679 in his presentation at the University of Leipzig, "Historico-Dissertatio Philosophica de Masticatione Mortuorum" also known as "chewing Mortuorum", describes in detail the behavior of those dead.
The theologian describes and justifies the phenomenon of vampirism as demonic possession and each considers unjustified violent action against any action against them as a corpse is nevitably an action against God and therefore to be condemned.

During the Middle Ages, the lack of scientific knowledge of plague determined the frantic search by the populace of "carriers" of the disease, which in turn were identified in weak subjects, and especially among women.
Therefore, those of them who died uttering a stream of blood from the mouth (hemoptysis), a feature also of the pneumonic form of plague, were considered "vampire." " (quoted at amazon.com)