Hawthorn is supposedly especially dangerous for the undead according to Balkan folklore. Stakes for dealing with the undead would have been specifically made from hawthorn for its magical properties, although I think that little tidbit has been phased out in modern depictions.

When Petar Blagojevic, an infamous Serbian vampire, was staked, it was said that “when they drove a hawthorn stake through him, fresh red blood flowed from his mouth and ears”, so I assume it could also have the effect of bleeding out whatever blood it consumed.

As a side note, I find it interesting how vampires (weird bloated corpses that could fit through small holes like some weird gelatinous creature) have become more like dhampir (their half-human offspring) in modern media.