Eliminate vampire as a class or race. Same with lycanthropes. Make them MOBs. If you are killed by one, you get their curse. For vampires, it is simple. Extra powers, penalties in daylight, and a need for blood to stay alive. In this case the player has control but has to live with restrictions. Cured by "remove curse" cast by mid-level (to highest level possible) cleric.
For lycanthropes, the curse takes away player control when the weather/sky setting hits full moon. The player transforms and is a MOB for 2-3 real life minutes. If the player is killed he goes back to human form. Cured by a "remove curse" cast by a quarter-level cleric.