yearly rabies vaccination

Hey there,
The time has come for Chester to get his one year vaccinations. I tried reading some of the threads that have already been posted, and doing a search on the internet but I can't come up with an answer.
I asked my vet-assistant when I phoned to make the appointment (for later today) if it was a 3 year shot or a 1 year shot. She said it was a 1 year and that it had special adjuvants to not cause tumours. I asked about the 3 in one being given once every 3 years and she said "you'll have to talk to the vet when you come in about that".
Ok, so a few things to clear up. What's the difference between the 3 and 1 year shots? Can a cat still get tumours from a 3 year? If they can't get a tumour from a 1 year, is it ok to put it in the back of the neck, or would you suggest the leg? Chester is indoor only, and I can't find any local bylaws or provincial bylaws that say that rabies is required (although it should be). How often should a indoor cat have a 3 in one? What would you do?
My appointment is in about 3 hours, so I'd like to have a little info under my belt before hand.
Thanks a bunch!

At my clinic rabies is given as a kitten, at one year, then every three years after that. The combo vaccine (for leukemia, chlamydia, rhino...) is given every year. The reason we give it every year is because that is what the vaccine company says. They say that it has to be boosted every year to be effective. If you start giving it every three years you are using the vaccine "off-label" at your own risk. Having said that, many veterinarians are going to three year protocols and using the vaccines off-label. The vaccine companies themselves are even starting to test their vaccines and see how long they really last. A few vaccines have even been labelled for every three year use. You should really talk to your vet and see what he/she thinks.

What is ths about rabies vaccine causing tumors?