Some holistic veterinarians think all vaccinations are actually harmful and destructive (and ignore the fact that diseases such as smallpox and polio are almost non-existent today due solely to the use of vaccines to protect the population from the diseases). My personal belief is that we may not need to vaccinate dogs and cats yearly for a number of diseases.
Conversely, if the goal is protective levels of immunity, maybe we should vaccinate more often than once a year for some others (such as Kennel Cough).
But since I have no way to know which individual dogs/cats do need protection and what individuals do not need additional vaccination, I must take a stand for vaccinating to provide my patient (with the owners' informed consent, of course) with the best level of protection I have available.
And that is just to vaccinate. Through 38 years of managing pet diseases and seeing tens of thousands of patients live well into their teens that have had numerous vaccines almost yearly throughout their entire lives, I am not convinced by experience that vaccinating has a destructive effect on the overwhelming majority of animals.
I am, however, convinced that vaccinating has saved uncountable lives from the ravages of parvovirus and distemper... not to mention potential rabies cases. If a animal has an allergic reaction to a vaccine then obviously, a different approach is needed than to repeat that vaccine.
If I see a very old pet that has very little exposure potential to contagious diseases and that has been vaccinated numerous time throughout its life, I intellectually and experientially have less inclination to revaccinate that animal yearly. But I must assume it has some level of immunity because I have no way of really knowing.
In addition, older pets are known to have less potential to contract parvovirus and distemper. The rabies topic needs to be treated very carefully because any warm blooded animal of any age or health status has potential to contract rabies if exposed. Not to be forgotten, unlike some other animal diseases, rabies is nearly always fatal in humans.
The response above is my personal opinion, based upon 32 years of small animal practice and seven years of college study. My personal, experience-driven practice protocols may be different from another veterinarian's.
So the bottom line for per caretakers is this: In arriving at a decision about vaccinating your dog or cat, get the facts about vaccinations, listen to your veterinarian, then get a few other opinions from other veterinarians. (Remember that any individual could have an adverse reaction to a vaccine. If that does happen, of course it might be risky to revaccinate for that disease and it may be best not to vaccinate for that disease in the future.)
If someone tells you that vaccines cause disease or weaken an animal's immune capabilities, ask to see the data that proves that position. Then you make the call. You are the final authority regarding your pet's health care.
Once you feel you are comfortable with your assessment of the vaccine topic, no one should pressure you into doing something different.