I have a grey who is now 13.5 years old and two and 1/2 years ago she had a reaction to her vaccines even though they were given at three year intervals. She ran a fever, was lethargic and did not want to eat for about four days. The vet confirmed it probably was a reaction to the vaccines. She did recover without any problems but it was a scary experience. We do not give vaccines (other than rabies, because of state law) to any of our greyhounds over the age of six as a result of that situation.