i have run a LOT of vampires in tabletop games. including a few Champions system based chronicles.
my favorite game master had a "meta verse" of their own. every chronicle was a gem in the brilliant tiara of that meta verse. no matter the system. D&D, Champions, White Wolf, Call f Cthulu, and a few "we'll try this"
in that meta verse Vampirism was a "space virus" with a metaphysical component. and an extremely aggressive mutation rate. therefore a "strain of the virus" might act very differently chronicle to chronicle or bloodline to bloodline, or even radically shift character to character. we never explored the actual origin of the virus. but we did have a "Cain", in the champions chronicle world. who was teaching advanced mathematics at Miskatonic University. and was not fond of anyone/anything.