So, we have the vampire Sanguini who is briefly seen in Harry Potter and the Half-Blood Prince.
“Harry, I’d like you to meet Eldred Worple, an old student of mine, author of Blood Brothers: My Life Amongst the Vampires — and, of course, his friend Sanguini.”
"Sanguini, stay here!” added Worple, suddenly stern, for the vampire had been edging toward the nearby group of girls, a rather hungry look in his eye.
I haven't perused The Philosopher's Stone or The Chamber of Secrets (thoroughly) for quite a while, and I'm interested to know if there are any references or appearances of Rowling-vampires in there, or if Sanguini is the first mention of Rowling's concept of vampires.