Cats need to be vaccinated once a year for rabies for the first year and I think every 2 or 3 years after that. Distemper is given at 6 to 12 weeks of age and annually after that. Ask your vet. He'll be able to tell you how far apart the distemper shots are. The reason they need to be vaccinated is because, even though they may be indoor cats, they still can be exposed to other cats, racoons, squirrels, etc. And, it is the law that their rabies vaccination be current or you could be fined.
Hope this helps.
P.S. Distemper (or Panleukopenia)is NOT a fun thing. 75% of the kittens under 16 weeks of age die from it. I've seen kittens go from being active and playful one minute to lethargic, with diarrhea, vomiting high fever, dehydration and lack of appetite. They can die from it if not vaccinated. And the distemper virus stays airborne for 6 months to one year. It can remain in the bedding, carpeting, clothing of anyone handling the cat. The virus is resistant to many disinfectants. I know, I had it in my house. I was terrified to foster any kitties. You can also go into Yahoo and search for feline distemper. That'll give you a better idea about the virus.
Kittens should receive a series of vaccintaions. The reason they do this is to get their immune systems up so they can have them annually. This is the general schedule..
8 weeks..feline distemper and a de wormer
12 weeks...feline distemper, rabies, de wormer and feline leukemia if they are an outdoor cat.
16 weeks...feline distemper,and leukemia if they received the first one.
A year from the date you received the rabies, you would get the rabies, distemper and leukemia if needed. Rabies will vary from state to state, the local vets will know. The distemper and leukemia are given on a yearly basis. Hope that helps!!