I bred shelties and showed them all over the country for 25 yrs, they only ever had their puppy vaccines and first booster, I always felt they built up their own immunity. My cavs are 4.5 yrs and 4 yrs, they have only had the same puppy and first booster, they are fed barf diet which I believe strengthens their immunity, I do not believe in pumping them full of chemicals, so far no problems with autoimmune problems.