In most states the rabies shot is the ONLY shot that your dog MUST get... not that I've seen the rabies police come after anyone.... but... I wouldn't want to be the person of a dog who bites someone and their dog DOESN'T have a rabies shot.
My dogs get the 3 year rabies shot.... I think with older dogs you probably no longer have to have anything done because all the years of getting shots have made them immune to just about everything.
