Question about indoor cat vaccination

We adopted a brother and sister from the same litter of cats. They were 8 weeks old at the time and had their first initial shots. We finished up the first round of shots and then we had them receive shots at 1 year of age. They are now about 3 1/2 and we have never taken them back for more shots. The vet does have their records but they do not go outside at all and do not come in contact with any other animals. Regardless of local laws or ordinances, is it really necessary for our cats to have vaccinations?

 

Answer from Dr. Gaylord Brown:
Indoor cats should be vaccinated for airborne diseases every three years; after their initial series of vaccinations. Rabies vaccines should be given every three years as a matter of public health.