Seán Manchester (from his writings) on the parasitic undead:
The intended victim of a real vampire might fall under its malignant influence, but it would not be possible for someone to "change" into one while still alive. Enjoyable though Francis Ford Coppola's Dracula (1992) might be as a cinematic experience, it is not a faithful retelling of Stoker's novel and, even if it had been, Bram Stoker's original Dracula is not a faithful account of real vampirism. That notwithstanding, there are elements in both film and book, mostly the latter, which ring true.
The soul of an afflicted person who assumes death following the predations of a demonic entity is an interesting one which I discuss in my concise vampirological guide, The Vampire Hunter's Handbook (Gothic Press, 1997). I describe the undead as a fundamentally malevolent and parasitic force which manifests in corporeal form; a bloodsucking androgyne with foul appetites, and the most abhorrent and feared of all that dwells in the malign supernatural underworld.
Not everyone will agree with me. Some subscribe to the view that vampiric spectres merely masquerade as the deceased and that the soul of the victim is not involved. This is an easier option for demonologists to adopt and perhaps a more comfortable one theologically to explain, but I speak from personal experience and while the predatory wraith might very well assume different metamorphoses, it has the power to manifest as a corporeal form that is as tangible as you and I. William of Malmesbury in the twelth century tells of evil men returning to walk the world after they had "died" and been interred. He credited this ability to the Devil who caused the corpse's reanimantion and vitality beyond the grave. The significance of blood cannot be underestimated for the soul has its abode in the blood as long as life lasts. In Leviticus 17: 14, the soul is identified with the blood, as it is in Genesis 9: 4; Deuteronomy 12: 23.