My show didn't air until the late 90s, right? But this stuff has been going on forever, and with the whole time-travel-people-can-be-taken-out-of-their-timeline-at-any-point thing, it's possible they came in before my show and they didn't know they were vampires. Or maybe they didn't come through this portal. There was that hell dimension so it's possible that it could have been something like that too.