Kathy-- Your ferrets NEED to be vaccinated for CANINE Distemper with a Modified-Live vaccine of non-ferret origin. Two vaccines commonly used for this vaccination in ferrets are FERVAC and FROMM-D, both cultured from chicken-embryos. While vaccination for feline disptemper will not likely harm your ferret, CANINE Distemper is *EXTREMELY* fatal in ferrets-- they do NOT recover. This is the disease that wiped out the greatest part of the tiny population of the wild Black-footed Ferrets in Wyoming, and should not be taken lightly. If your vet wants to argue this with you or refuses to innoculate your ferret for canine distemper, FIND ANOTHER VET!! I personally suggest that you vaccinate the ferrets for rabies as well, once they reach 3 months of age. While your ferret is unlikely in the extreme to ever develop rabies (little, if any exposure to rabies vectors and relatively low susceptibility in ferrets), the vaccination may help to prevent headaches and heartaches should your ferret ever nip someone. There is a rabies vaccine licensed for use in ferrets by the USDA called Imrab, distributed by Rhone-Merieux. This is a KILLED VIRUS vaccine. DO NOT allow your ferret to be vaccinated with a live vaccine, as this has INDUCED rabies in ferrets! Insist on Imrab, or at the very least, a KILLED virus vaccine. The ferret dosage is 1 ML under the skin. Best of luck, Debra in Ft. Worth, TX [Posted in FML issue 0808]