>>16072
Needing permission to enter isn't exclusively vampires. It also appears sometimes in old fay folklore, which I think the BEK are more likely related to. Fay tradition also has changelings, so one could easily speculate a connection.
More tenuous but I'm also reminded of the whole "demonic contract" idea, where you basically "invite" demons into your life in a more general sense. Lots of stories all around where evil needs a foot in the door before it can really fuck your shit up.