In Christianity, one of the most sacred objects is the eucharistic wafer. The wafe is a symbol of the body of Christ, and together with wine (the symbol of the blood of Christ), it is taken during the Holy Communion of the Eucharist. Older religions such as Roman Catholicism look upon the eucharistic objects as being mystically empowered by the spirit of Christ.
Because of its apparent mystical powers, the wafer was often used in ancient times for other purposes. It was used both in burial when the deceased had lived an evil life, and to ward off spirits. Many historical religious papers cited these other uses for the wafer. It's believed that Bram Stoker used these papers as a basis for the wafer's power in his book, Dracula. In the book, Abraham Van Helsing used the wafer many times; it left a mark on Mina's skin when held to her forehead, and Von Helsing used it to seal Lucy's grave until he could return to kill her.
Since Dracula, the wafer has been used only rarely by those wishing to ward off the vampire. It has been largely substituted by the cross, which has picked up one of the wafer's qualities; the ability to burn vampire skin.