This was pre-Bram Stoker, more than 120 years before the birth of Anne Rice, and all the others that followed. Polidori based Lord Ruthven on Lord Byron. I published this review of the short story on Amazon last week:
If you’re looking for a quick, classic gothic tale, why not pick up the one credited by many for the birth of the vampire genre. Before Bram Stoker’s Dracula there was John Polidori’s Lord Ruthven.
I’ll leave out the details and let anyone who stumbles upon this review discover the rest. This short story is worth a read.