Or if a vampire bites a werewolf?
A vampire will not transform into a werewolf if bitten by a werewolf as humans do. Vampires are already dead, or living dead to be precise so they cannot be transformed into a living dead werewolf. Although it’s really the overwhelming power of the vampire DNA that resists the supernatural lycanthropy virus that lives within the werewolves saliva and bloodstream. Werewolves ingesting vampire blood will weaken, have hallucinations, and other random symptoms. They will usually run away from the vampire as it feels it’s power slipping away. However this only lasts for one or two nights.
If a vampire bites into a fully transformed werewolf then it becomes more aggressive and oddly enough develops an aversion to the moonlight. Within hours the vampire is back to normal. Realistically vampires are disgusted by werewolves so it’s not likely they’d bite into one unless they were in a battle with one or most likely more since vampires are stronger than werewolves. Hypothetically if a vampire went through the process of turning a werewolf into a vampire by nearly draining them of all their blood and then introducing vampire blood it would probably just kill the werewolf rather than create a vampire werewolf hybrid. However if a vampire attempted to bring the werewolf across in it’s human form, there is anecdotal evidence that a hybrid could be created. The person would be vampire all the time except on nights of the full moon when it would transform into a super vampire werewolf. However the mental powers of a vampire would eventually allow it to control it’s transformations at will.