well isnt the feline HIV similar to human HIV? if so how in the heck could a shot help to prevent spreading the disease to another cat.. lol it doesnt work that way for humans.. so therefore you are letting this cat spread diseases to other cats.. then one day the cat doesnt come home because its dead on the side of the road somewhere.. having other animals pray on it.. sounds to me like you are unresponsible.. you should have never taken on the responsibility of taking in the cat in the first place if you couldnt care for it properly.. at least take the cat to a rescue or something..