We have our Greyhound's blood 'titered' when a vaccine is due. "Titering' will tell the levels of anti-bodies still present in the blood and will determine whether a vaccine is needed or not. We've, so far, only needed Rabies vaccination, but this is also by law in our county.
Some animals may NEVER need to be re-vaccinated for certain things, our dog's vet told us. She's also a holistic DVM.