My Luke had a bad reaction the the Feline Luekemia shot. I found him stretched out in the bath tub gasping for breath. I had to take him in and they gave him a shot to counteract it. Leonardo had a huge lump come up under one of his front arm pits after his first Feline luk shot. Luckily it went away in time. I refuse to let the vet give that shot to the boys now. They've all been tested and are negitive for fel lukemia and since they are all indoor cats I just don't put us through it. Usually after their regular shots they may droop around that evening but are fine the next morning.