Watts did a whole academic presentation on the science of vampirism in the book's context. It's a fun watch and makes it feel much less random. https://www.youtube.com/watch?v=wEOUaJW05bU
If you want a really shoehorned scifi vampire, there's a David Weber book in which it comes out of fucking nowhere towards the end.
If you want a really shoehorned scifi vampire, there's a David Weber book in which it comes out of fucking nowhere towards the end.