My vet told me the same thing. She says that the Feline Leukemia Vacination could have too many harmful side affects and doesn't recommend it unless you have allow your cat outside or near cats that go back in forth. She says its just a risky thing in her opinion and there are still things they are learning about Feline Leukemia and the vacinations. She said it is one of the most harmful vaccinations. I opted not to have my inside cats vacinated for it for that reason.