Normally, you would get a booster shot in your arm.

he does not need a booster...they have found that one shot works

A Booster raises money for a cause.

OR A Booster shot is used to build up immunity to protective levels.

a booster is just an informal name used to refer to the shot that was initially given to your dog a year prior. It can be a distemper or rabies shot or another shot. booster is just your dog needing to be re-vaccinated since most vaccines only last for one year