Board Thread:Skyrim/@comment-108.93.192.237-20150506235526/@comment-6881629-20150507094412

Without Dawnguard a Vampire thats reached level four will be attacked by almost all npcs's on sight, you have to feed regularly to stop it from happening. With the dlc that no longer happens as a Vampire clan is one of the two opposing factions you can join. It could also be because of a bounty you have so then you'd need to clear it if none of the above try going away from them and waiting a few days.