All the above but this is a good plot for an adventure. I would let the player slowly be affected by the vampirism, minuses during the day, adding the template at night. Rolling a save everyday or become one. Rolling a save against the hunger or start biting the other players.
Your real problem is he has become chaotic evil! (If you play it that way). I would use a flow chart with the end result being CE and steps to it, have the player roll a save everyday if he fails moves one step closer.
Create a side adventure, a shrine, well or spring that has the ability to cure the player (if they can make it in time) and run it. It becomes the players have to help their party member, they have to deal with someone that may be seeing the changes as a good thing. No big monster other than the player and the journey.