Major Changelings (and presumably vampires) aren't immune to diseases

[warcrimes]

No not feature, "feature".
and a big fuckin' mood too.
It should maybe be changed but not necessarily fixed imo, there's mad flavor in a DNA monster that rearranges its proteins at will getting a prion infection and having all its body parts start shitting the bed, maybe less devastatingly but dropping limbs constantly sounds like fun.