The CDC endorses the Compendium of Animal Rabies Control, 2001. Then once yearly. Then once yearly. For older ferret or history unknown. On first vet visit Repeat in 4 weeks.
Ferrets have a tendency to develop more allergic reactions to vaccines as opposed to dogs and cats.
You should stay at your veterinarians office for a minimum of 30 minutes after vaccination and closely monitor your ferret for several hours. If your ferret has a severe reaction, you need to consider whether you should vaccinate your ferret at all.