Without wanting to pre-empt the story, you might as well know that vampirism doesn't work quite like an infectious disease in the Buffyverse - the vampire has to drink most of your blood, force you to drink some of its blood to make sure that your corpse will be animated by a demon, then finish the job of killing you. If you don't die immediately you don't become a vampire.
Werwolves, on the other hand, are infectious but not fundamentally evil, just very active predators - Oz, a regular in the show for a couple of years, was a werewolf who was infected by a nip from his cousin when the cousin was a little boy, don't think we ever learned how the cousin was infected. Oz locked himself into a cage at the full moon to avoid hurting anyopne.
Now were-Jimmy might be fun...
