You can get vampirism cured in game.
From UESP:
After the first three days of infection, or if you obtained your vampirism from Lord Harkon or Serana, the task of finding a cure becomes more complex. While visiting any inn, talk to the innkeeper and he or she will send you to
Morthal to speak to a man named
Falion. This will start the quest
Rising at Dawn. However, if you are in the last stage of vampirism (and do not have Dawnguard installed), the innkeepers may attack you on sight, so you may need to feed in order to lessen the effects of your vampirism, making NPCs friendly again.
You can also cure your vampirism by becoming a werewolf through the
Companions faction. However, once you contract lycanthropy, you gain a 100% resistance to disease and cannot be re-infected with
Sanguinare Vampiris by normal means while a werewolf.
With Dawnguard installed, if you were previously a werewolf at some point prior to becoming a vampire, then you can ask
Aela to restore your lycanthropy once, which will cure your vampirism (by making you into a werewolf).