I only bought it for the neighborhood & deleted the original vampires. One or two have shown up since then, but they haven't been a problem. I had one incident where a sim couldn't leave a bar, because a vampire was breaking in, but other than that, my sims have had no run ins with them. They don't overrun the town like they sometimes did in 3, so it is pretty easy to ignore them if you want to. Adding "private dwelling" to your home lots traits does help keep them from breaking into your sims' house. Most of the time.
