What happens when a human bites a vampire? Does the vampire turn human?
In a few cases, vampire is a corpse and some of them are as hard as stone. Human biting vampire would break their own teeth.
In other cases, humans would feel like they just took a bite out of ash.
Vampires vs Werewolves
What went wrong and why? Why is there usually some kind of big enmity between the two groups?
Potentially, rivalry between predators within the same territory.
Another answer is how the dynamic between ww, human, and vp works.
Vp needs human blood. Ww doesn't need human flesh but ww bite turns humans into ww -> less blood for vp.
Could also be problem down the line. Certain vp came from wolves. Ww also came from wolves. Thus, they are sister species. However, just because they are the same doesn't mean they should be cordial with each other. Racial problem is not something unique to humans.