[Snake]

Treated wounds will still make you get fever.

Fever affects Vampires, even though they're supposed to be resistant to illnesses. (Or maybe I misread it, being resistant and immune might be two different facts. That is up to you to decide.)

I presume this might also happen to other races which are by logic immune to it (such as Mechanation, for example), but it's just a speculation.

[Neus]

Are you sure the wound was treated before you got the fever?

[Lonestar]

I can confirm. I also got a fever with a treated wound.
EDIT:

[Neus]

This has been corrected.