Since the 1970s, the professor and chair of pathobiological sciences at the University of Wisconsin-Madison School of Veterinary Medicine has been studying canine vaccines and has found that dogs are being over-vaccinated.

As a result, a group of canine vaccine experts has developed new veterinary guidelines that may eliminate the need to give annual shots to dogs.

Dogs receive up to 16 different vaccines each year, often combined into one shot. While four of the vaccines protect against serious diseases like rabies, canine parvovirus type 2 (CPV-2), canine distemper virus (CDV) and canine adenovirus type 2 (CAV-2), the others protect against much milder diseases that a dog may or may not be exposed to, such as Lyme disease.

However, over-vaccination can result in side effects such as skin problems, allergic reactions and autoimmune disease. Moreover, tumors have been found at the site of vaccine injections in cats, though not dogs.

The adverse reactions caused by vaccines have caused many veterinarians to rethink the issue of vaccination.

Evidence suggests that like humans, dogs could be vaccinated with certain vaccines early in life and be protected for a lifetime, rather than receiving yearly doses.

Reportedly, with the exception of rabies, the core vaccines, which protect against life-threatening disease, could last for seven years and should not be given more frequently than every three years. Rabies shots have a three-year duration, according to research, and should be given every three years.

In terms of the non-core vaccines, many have a shorter duration and last about one year. But according to researchers not every dog should get these vaccines because only some dogs are at risk of exposure. These vaccines, such as the shot for Lyme disease, can cause adverse effects and should only be given if the dog is at significant risk, as is the case with all vaccines.

Many veterinarians rely on annual vaccines to bring in income, so the revised recommendations may create controversy. However, researchers note that annual visits are important for other reasons such as checking for heartworm and tumors. A recently developed test can be used to check dogs’ immunity against certain diseases rather than vaccinating them each year.

Additionally, researchers say that veterinarians who have switched to three-year vaccinations, as opposed to annual vaccinations, have not had seen an increase in dogs with diseases that could be prevented by vaccines. Further, giving an animal a vaccine that's not needed creates an unnecessary risk to the animal.

Journal American Animal Hospital Association March-April 2003;39(2):119-31