I'd like to believe they're real. I mean, there's so many folklore and mythology on not just vampires, but many other supernatural creatures. They must have come from somewhere, right? What if they all used to be real but then became extinct? It's plausible, innit?
Yes, I believe there are human-like beings that are immortal if they suck human blood, cannot tollerate the sunlight and can be killed with cross shaped sticks.