The booster is then repeated annually to ensure continued protection. In most states, it is a law that your pet be vaccinated against the rabies virus. The rabies vaccine is also required for international travel with your pet, and the timing may be important, so check before you go. The rabies vaccine is also a legal issue if your pet ever bites a human. If a dog that is not up to date on his rabies vaccine bites a human, he will be subject to quarantine.
Rabies does exist in the U.S., especially in the wildlife population, so it is a real threat.
I get vaccinated against rabies because I am in a high-risk occupation. Interestingly, the horror stories about the rabies shot for humans don't apply if you have a pre-exposure vaccine. It's bad if you have to get vaccinated after the fact, as the shot is routinely given in the abdomen. I consider some vaccinations to be optional, depending on your pet's individual exposure. If you frequently board your dog in a kennel or spend lots of time in a city dog run, be sure to get a kennel cough or bordetella vaccine every 6 - 12 months.