Here are the facts on felv vaccines. I just got this info from my vet in canada. My 2 year old Vixen is felv+ and we wanted to know about getting another cat so here is what we were told.

40% of all cats are natually immune to the felv virus. Out of the 60% of remaining cats that can contract the virus approximately 85% of these when vaccinated the vaccine holds. In other words the vaccine works on 85% of the vaccinable cats. But that leaves about 15% that even when vaccinated will not respond to the vaccine and will remain at risk. So it will be extremely risky for the 15% of the 60% that are not natually immune to contract the virus if in intimate contact with an infected cat. This virus can only be contracted through intimate contact. Being though blood, urine or feces, inter-grooming between infected and non-infected, scratches and bites. I was told it is similar to the HIV virus in humans. Stress is also a factor for the felv+ cat. minimal stress is suggested. If the infected cat is stressed a lot by change and newcomers into the home it is not suggested to take on another animal. Mainly for the well being of the felv+ cat as the immune system is so delicate in the infected cat. I am sure there is more I am not thinking of right now but will let you know if I can think of anything else. Also, if you want I can contact my vet and have him forward all info to you on this matter.

Michelle