You lose all vampiric advantages once you're cured, and the only quest that requires your character to be a vampire is the one for the cure.Does the 100% Resist Disease remain after you've been cured?
Are there any quests that require you to be a vampire, or any that cannot be done after being cured?
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You can do any of the other quests as a vampire or a normal person. Heck, there are certain quests that, by common sense, a vampire shouldn't be able to do (Order of the Virtuous Blood, Azura's Shrine, and Information for a Price) that the game still allows a vampire character to pursue.