Ours have always had their boosters, but at the moment, Blue's in a very bad way with a diagnosis of autoimmune disease. He's on steroids and has had a blood transfusion but over the weekend we'd decided to have him put to sleep at his vet appointment on Monday morning, so stopped his meds. The vet thought Blue had a bit more pink in his gums and checked his red cell count which had stabilised and suggested stopping the Atopica steroid all together. The upshot is, we still have a very sick dog but he's holding his own at the moment. Googling autoimmune disease in dogs led to a site that was linking the disease to the application of topical flea/tick treatments which he'd just had, but having said that, his brother had the same treatment and is fine, so what are you to do ?