If your vet isn't rethinking the frequency of vaccinations, more and more owners certainly are.

The idea of injecting multiple biological agents into Fido year and year has made many people wonder what is happening to Fido besides hopefully gaining immunity to the diseases.

Note we are arguing only about boosters, not puppy vaccinations. Once the series of puppy vaccinations is complete, the question remains how often and for which diseases a mature dog should receive boosters.

Most veterinarians today seem to agree that if a vaccination isn't necessary don't give it and that dogs are likely to be over-vaccinated.

Unfortunately all dogs potentially come into contact with diseases even if they never leave their homes.

You could carry most of these diseases to your dog on your shoes or they could be transmitted by other animals such as mice or rats. Air currents and inanimate objects also can carry disease.

Louise Louis of www.ToyBreeds.com offers some commonsense points to help your decide.

1. Are there diseases prevalent in the area in which you live? Are they treatable?

For instance, most vets don't recommend vaccinations against Lyme disease unless you live in an area where it is prevalent. Lyme disease also is easily treated with antibiotics should Fido develop it.

On the other hand, you may want to take a conservative approach on a disease as virulent and highly infectious as parvovrius or distemper.

Even if the dog survives an attack of distemper, he is likely to suffer permanent impairment of the nervous system.

The conservative approach for mature dogs is to vaccinate annually against parvovirus, parainfluenza virus and leptospirosis and every other year against distemper and hepatitis. States usually regulate how often rabies vaccinations must be given.

2. Is your dog otherwise healthy?

Vaccination of sick animals is rarely a good idea and vaccinations may exacerbate any existing illnesses. Some medications affect a dog's response to vaccinations and may reduce the dog's ability to respond to a vaccine.

3. What is your dog's lifestyle?

Do you take him to dog parks? Does he board at kennels or participate in dog shows? Obviously, the more social the dog, the more likely he is to come into contact with disease.

Talk to your vet. There are potential risks as well as benefits. Your dog's health depends on your decisions.