In The Dresden Files RPG, Red Court Vampires(RCV)/Infected have the supernatural power Addictive Saliva (YW162). The power itself does not say anything about it conferring immunity to the saliva of other RCV, and the books don't address that either.
Is there any rule/reference that I might be missing that would say for sure if they are or are not immune to the effects of the saliva of other RCV?