are annual vaccinations good for dogs?

A visitor from Canada recently commented to my sister that Australians over-vaccinate their dogs. She was surprised that we give our pets vaccinations that she considers unnecessary.

Penny still gets her annual shots because I take my vet's advice, but at an online magazine called Dog Owner's Guide I found an article that has got me thinking.
The article discusses at length the pros and cons of vaccination regimes. In part it says:

Research shows that vaccines have a longer term of effectiveness against disease than previously thought, and some veterinary colleges have published alternative vaccination protocols that suggest three-year intervals after the initial shots and a 12-month booster...

An increase in knowledge about the canine immune system and more information about the length of time that immunity is conferred by particular vaccines have prompted veterinarians and researchers to question the yearly booster for adult dogs.

As a result, several universities have changed their vaccination recommendations and both the American Veterinary Medical Association and the American Animal Hospital Association have published changes in their vaccination guidelines.