My impression is that the werewolf transformation is entirely magical and not governed by real-world effects: one moment, the moon is out and you suddenly grow fur, a snout and uncontrollable predatory instincts, and when it’s over, the fur recedes/disappears, your facial geometry is restored and you just feel inexplicably tired. It’s conceivable that you’d shed some hair, which presumably wouldn’t magically vanish once it’s not attached to you, though.

As for vampires, I thought they just used their incisors to puncture their victims and then just sucked their blood out. Their teeth being plumbed into a vacuum pump seems somewhat too complicated.