I purchased a purebred male Russian White feline, DOB 3-26-17. Brought him home at 8 weeks old. Beautiful, extremely energetic, playful and very affectionate. Gave him the recommended vaccines at 10,12,16 weeks. I separated the Rabies to give it by itself as well as the first feline leukemia vaccine, 2 weeks after rabies. All vaccines before the FeLV seemed to agree with him. About 1 hour after the first FeLV shot on Aug 21st, he was lethargic and just plain didn't feel good for about 36 hours. Then 3 weeks later I let the vet give him the booster. He quit playing, just wanted to sleep and be held. Then, about 2 weeks later he developed severe diarrhea, had blood in the stool, and vomited several times and virtually stopped eating. After numerous attempts to find something he would eat, he seemed to feel really hot, so I took him back to the vet on Sept 21st and $2200.00 later, I still had no definitive diagnosis of what was wrong with the little fellow. He still, at 6 months old, didn't weigh 5 pounds yet and was getting worse. Vet wanted to send me to an internal medicine specialist so they could "do more tests" when I knew in my heart that it was a severe reaction to the FeLV. Things were way too coincidental with the timing of the vaccines. I agreed to take him to the internal medicine specialist, first available appt was for Nov 9th. I took him to a second vet in the meantime on Nov 1st, thinking he was constipated since his little belly was very distended. This vet did an abdominal tap and found fluid and blood in the peritoneal cavity. Not a good sign. Gave rectal enema for some relief and low dose steroid shot. I tried everything, even water with baby syringe. He got weaker and weaker. He died Nov 4th before I could get him to the specialist.
If you are thinking about giving the FeLV for your indoor only cat, I hope my experience will help you make your decision easier.