The Rabies shot is the same, whether it is given annually or every three years. It is generally safe, but if you are worried about a reaction, you can stay at the vet for half an hour to be sure. Fortunately, none of my Yorkies ever had a reaction from the vaccine, but other dogs have on YT.
This is an excellent resource to read about vaccines.
vaccine1.htm Dr-Dodds-ChangingVaccProtocol