I have never had a Vampire break in - and oddly if they did I wouldn't care really as I am fond of the Vamps. I think my problem stems from the fact most of my sims are Night owls so they are never asleep when the few times a Vamp showed up. The most I have happen is the Vamp acts like a peeping tom and keeps watching my Sim through an outside window. Makes me wish these Sims could learn Martial Arts and go out side and attack the peeping Tom. LOL.
Usually though the Vamp gives up waiting for my night owls to go to bed - and they just take off around 3-4 am. But no vamp will ever break in as long as a single Sim is awake in the house. They want everybody in the household asleep and in my Sims houses that is highly unlikely before 3 am. LOL
ETA - I do not know if pets or infants affect this as the few houses I saw a Vamp peeping through the windows of had neither.