Booster shots are are not necessary for most dogs. In fact, boosting your dog regularly (according to the AKC guidelines) could be harmful.
Vaccines work by showing the body a microbial mugshot of a microscopic perpetrator like a virus or a bacteria that poses a threat to the body. This causes an immunological fire drill against the perpetrator, which provides practice for when the body is fighting off a real attack, ideally much faster and quickly. This immune response causes side effects (Read more on that here). The more your dog is vaccinated, the more likely it becomes that he/she will develop vaccinosis, which is an adverse reaction to vaccines. You can read more on vaccinosis here.
Veterinary immunologist Ronald Schultz, PhD, chair of the Department of Pathobiological Sciences at the University of Wisconsin researched the duration of immunity for the distemper, parvovirus, adenovirus and rabies vaccines.
His immunology research proved boosters aren't necessary in the 1970's and confirmed that that immunity lasts for far longer than pet parents are told. Once a dog has received initial shots, they will continue to be fully protected without the booster. According to his research, here's the minimum duration of immunity for canine vaccines:
Distemper – 7 years by challenge/15 years by serology
Parvovirus – 7 years by challenge/7 years by serology
Adenovirus – 7 years by challenge/9 years by serology
Canine rabies – 3 years by challenge/7 years by serology
Challenge means the researchers exposed the animal to the disease and serology means they measured blood antibody level (Source: Dogs Naturally).
Dr. Schultz stated, "vaccines for diseases like distemper and canine parvovirus once administered to adult animals, provide lifetime immunity." You can read more about his comprehensive research here.
His work has also been verified by the work of other immunologists including, Dr. Ian Tizard concluded that "in a patient that has been previously immunized, antibodies from the previous vaccine will block the replication of the new vaccinal virus. Antibody titers are not significantly boosted. Memory cell populations are not expanded. The immune status of the patient isn’t enhanced" (Source: Dogs Naturally).
In other words, vaccinating more often does NOT mean your dog will be more immune.
This research has been around for over 30 years. There is literally no scientific evidence to vaccinate frequently. This isn't new information. So then why do vets recommend booster shots all of the time?
Well, for starters, the veterinary industry industry is monopolized by sugar companies like Mars Inc., and Nestle who are literally in the business of making money, which means keep animals alive, but not curing them or keeping them healthy. Vet schools are funded by the dog food guy, the dog food guy is also owned by the vaccine guy and the vaccine guy makes the laws on what makes what legal and what is approved. The dog food guy is also friends with the vet board guy because the vet board guy is funded by the vaccine guy.
The VCA states, "there is no evidence that annual booster vaccination is anything but beneficial to most dogs. Published research has shown conclusively that abstaining from some boosters can put your dog at risk" (Source: VCA). This is not at all surprising because the VCA is owned by Mars Inc. The same company that makes kibble, donates to vet schools and most probably sponsors vaccine companies in some way.
The VCA didn't reference any published research, so I did some digging and didn't find this magical research they were referring to. In fact, one study stated, "it is therefore possible that animals without or with low antibody titres are in fact protected. Serological tests are an option if owners are unwilling to have their animal boostered without evidence that it is needed. However, the cost of these tests is likely to exceed that of booster vaccination for the foreseeable future" (Source: PubMed)
When it comes to vaccination, ask for titer antibody blood tests to be done before giving anything. If your dog is sick or chronic condition, do not vaccinate after initial vaccines. Please refer to Bobzilla's recommended vaccination schedule here.