I might be completely wrong in saying this as I haven't played in over a year...
But I do recall there being an increase to damage received from poisons whether you are in Werewolf form or not.
I also recall personally choosing the Wood Elf (Bosmer) as my Werewolf due to their Passive Ability to Resist Affliction, increasing poison and disease resistance by a small amount based upon the characters level.
The Vampires had a similar increase to damage received from Flame abilities whether you are transformed into a Vampire or not.
The class I chose for my Vampire was the Dark Elve's (Dunmer) as they have a racial passive to resist Flame damage by a small amount based upon the toons level.
Again, I'm not certain as things have changed greatly since I last played, but I personally think of these as subsequent passives to being a Werewolf or Vampire.
Bye and have fun out there.