a vampire would likely be unable to pass a mezzuzah, even if he was invited into the house

That's why a well-prepared vampire will plan on bursting through windows after having been invited in, and will bring along a sledge hammer to go through the walls. On the plus side for the people in the house, if the walls are lath and plaster, the bits of lath might be useful as improvised crosses, which is ironic, but any port in a storm.

Personally, while 'Day of the Jewish Vampire (Which Starts at Sundown)' might be interesting, I'd rather see the other half of the double feature: 'Frankenstein's Monster vs. the Golem.'