When adopting my cat 3 years ago I was surprised to hear the vet say that she would need an annual rabies shot every year for 3 years and then one every three years. Cats used to get one rabies shot as a kitten that lasted a lifetime. So what caused the change? Does anyone know? Is this just a "lets support our local vet" thing or is there a scientific basis as to why one shot for life no longer sufficient?