My experience is this: nearly 15 years ago, my oldest male Vizsla had his 'last vaccination'.  All I can say is he was so poorly afterwards. Site of the needles was swollen & he was off colour for quite sometime.  From that time onwards he paces. Walks around, around around in a kinda aimless manner. 
Vet I spoke to then suggested he had had a reaction to the vaccination. No, we did not blood tests at that time. That vet THEN suggested to never vaccinate again. He explained the concept of doing blood serum levels to determine if the dog had protection against different diseases.  I did a whole heap of research. I was beyond shocked to read what was happening to poor dogs given does of chemical poisons. 
Dogs have never been given poisons since.  They have had a combination of conventional & holistic medicine.  In a space of 15 years, they had fleas ONCE. They were healthy enough, as borne out by their 6 monthly check ups.  
For me I have been lucky to find more than one Vet totally receptive to what 'I' want for my dogs, aka my fur-kids. I noticed in the thread mention of the Russell Lea Clinic. Outstanding place. The protocols changed for vaccinations. Not all vets moved with the times. 
Since 3 year boosters are suggested & titre testing it's better for people with aging dogs to be aware of not overloading their systems. The durgs are poison even if they prevent illness. It's that fine line isn't. 
Just my experiences. I am happy with what I chose to do. The dogs were healthy and happy,  :D