A mod which either removes the cure to Vampirism or make it significantly harder to achieve.
Maybe I just remember things wrong, but to me it always sounded like it would be hard for other vampires to cure themself, and then there I am, switching between Vampire, Werewolf and Dragonborn as I please because I either go to the Companions to become a (disgusting) Werewolf or just let myself be Cured from a rumor I've heard in an Inn.