If you have a dog that has an unknown vaccine history, or there is a concern that the dog may have a reaction to the rabies vaccine for whatever reason.
Talk to your vet, my vet gives my dog a shot of prednisone every three years just prior to receiving the mandatory rabies vaccine. This will block any acute reaction to the vaccine for 24 hours. One shot of prednisone should not hurt an otherwise healthy dog.
Not sure if all vets will recommend this, but mine did. I have noted no adverse reactions.