B e very careful when it comes to vaccinating you cat. Often times a vet will push vaccinations that are not neccasary, especially for a in door cat.
It is also a good idea to avoid the 3 in one type shots.Instead get one at a time, and give your cat some time in between shots to rebuild his immunity.
Do not vaccinate your cat if he is sick or particularly stressed,wait until he is better (unless you vet has a very good reason not to wait) Also be very careful about vaccinating older cats.
Vaccinations can and do save the lives of cats, but when used improperly chronic health problems and even death can result!