How often you vaccinate is determined by the law in your state. Some states don't have the option of a three year rabies booster. You can look up the rabies law in your state here:
http://www.animallaw.info/articles/a...atedoglaws.htm
What many people don't realize is that the same formula is used whether or not it is a one year or three year booster. They are just packaged differently to satisfy different state requirements.
This was printed in the Wall Street Journal on July 1, 2002:
One company, Pfizer Inc., decided to test its one-year rabies vaccine on live animals and discovered it lasted for at least three years. It sells the identical formula simply packaged under different labels — Defensor 1 and Defensor 3 — to satisfy different state vaccination requirements.
Considering the possible risks and side effects from rabies shots, it's horrible to think that in some states we are forced to over vaccinate our pets.