Magick cannot do physical change, therefore you can't become a vampire. Physically most people don't believe in them because a. no one's ever met one and b. there's historic/scientific explanations to vampires. The only one most give a pass to is astral. [Vampires are from another plane, but they aren't physically real] keep in mind the astral isn't universally believed in, but if it's real, vampires would be like spirits/energy.
Personally I leave a small sliver of hope mythological creatures [Vampires, werewolves, meremaids] are real, but I'm 99% certain they are not. Either way, you are human, and because magick cannot contradict nature, you can never become a vampire.