I will add to the very good and complete comment here above, that I go to the families management tool using cas.fulleditmode and change the vampires skin color to grey and undo their specific makeups and facial vampires traits, so when my sims encounter them I know it's a vampire without the vampire's looks and keep away from speaking to them.
I do play with vampires, but for some families I wish a more realistic way of playing. So, for these families, I see vampires as some kind of freaks, and when they break in (very occasionally) I just pretend it's like a home invasion from some sort of a weardo.
To me vampires (violent) and aliens (hiding who they really are) are metaphors to the kind of people I wouldn't want to have in my life.