my cat got leukemia from the vaccine. Rare, but it can happen.
There is a vaccine for feline leukemia and I recommend it for all my feline patients who go out. It is especially important for a cat who is not spayed since feline leukemia virus is readily transmitted by sex, and yes it can be transmitted to the kitten, but not always. It would be best to test the kitten for the feline leukemia virus after 12 weeks of age, but preferably after 16 weeks for the most accuracy. If a kitten is tested prior to 12 weeks and tests positive for feline leukemia there is a chance that the kitten could sero-convert and test negative later on, but not always.