For many years veterinarians have been recommending yearly vaccinations for our beloved pets claiming without these yearly boosters our pets will not be protected from disease. In my research I have found this to be true since the 1950’s. Over the years many veterinarians were suspicious that the vaccines used were giving much longer periods of protection than one year. They new this because they never saw distemper, hepatitis or provirus disease in dogs that had been vaccinated for many years. Many veterinarians tend to think they are undercharging for complex surgery and subsidize those procedures with the money they earn on yearly vaccinations. No one knows how this practice came about but it has existed since the 1950’s.
Manufactures also gave an incentive to veterinarians and still do, to sell more vaccine if boosters were recommended annually as well as a one-year mind set among the bureaucrats that staff the USDA Center for Veterinary Biologics that dictate vaccination protocols. These are the same deep thinkers that put a two-year expiration date on a vial of water.  Our veterinarians also get the same incentive protocol  when recommending the foods they sell.
Do the math; veterinarians have clients coming into their practice every day for boosters; if we stopped doing yearly boosters It would cut their income more than half.  It would decrease the side effects; remember the immune system of your pet is stressed by these vaccinations. "Dogs develop allergic reactions, facial edema, enteritis, lethargy, fevers, pruritis, nausea, coughing, seizures". It is also suspected that vaccinations can trigger certain autoimmune diseases such as Addison’s disease in dogs. Many times these reactions are life threatening. Vaccines contain many ingredients besides the dried virus. Some of these, antibiotics and adjutants (enhancers) are implicated in vaccine reactions.
Approximately 1% of dogs adverse reactions are reported yearly; this being low because many veterinarians do not report them to the proper authorities and find excuse after excuse to convince the pet owners that the reaction is not caused by the booster. Reason being they know most pet owners will make the decision to STOP these yearly boosters. As humans we vaccinate our children but after our series of boosters we do not need more yearly boosters throughout our lives.  This is true for our pets also but if our veterinarians were honest with us it would cost them hundreds of thousands of dollars
in booster costs. Yes vaccinations cause reactions and diseases in our pets; if we did not vaccinate yearly there would be less medical problems and no need for additional vet visits aside from their yearly check ups and unexpected emergency care.  
Several years ago I myself had brought two of my puppies to my vet for booster shots; right in front of my vet both puppies started to shake, shiver, foam from the mouth and collapse. The reaction happen just minutes after they were vaccinated and my vet shrugged it off and refused to fill out the proper forms and send them to let the proper authorities to let them know both puppies had sever reactions to the vaccination. Needless to say that was the last time I ever used his practice and started my research on Vaccine Reactions.
Since our horrible experience I have stopped vaccinating my Pugs; aside from my Sierra having Psychomotor Seizures and Camara who in 3 years has had 2 Partial or Focal Seizures (Petite Mal) all 14 of my Pugs are in excellent health.