"Are you now or have you ever been Vlad?"
An interesting, creative concept for sure, though like a previous comment said it could be made a bit more interesting with variations in how a vampire would appear in the mirror. I felt like having that would make it even more interesting.
Also, there are no consequences for just randomly clicking on everyone on the screen until you find the vampire. Humans don't fear the garlic stick, I heard some of them even make garlic bread out of it...