To Bill and Clare Sebok - Concerning your recent experience with potentially life-threatening reactions to Fervac-D, I must admit it is interesting that two of your threee had vacine reactions within hours of each other. Vaccine reactions are uncommon in ferrets and other animals. Fervac-D had occasional eactions in the past (a bit higher than normal) but supposedly has been reformulated to eliminate most of the problems. Perhaps your pets were vaccinated with an older batch... Concerning prevention of reactions in the future - many vaccines have the same ingredients, so switching back to Fromm D, although advisable, is still not adequate prevention. On your next trip to the vet, I would suggest that you remind him/her of your ferret's problems and administer a dose of anithistamines 30 minutes prior to the vaccination. Vaccine reactions in all species strike unexpectedly, usually with no prior warning. The animal has become sensitized to some part of the vaccine - only rarely it is the virus itself, more commonly it is another inert component of the vaccine. Probably, we miss most of the allergic reactions, and only pick up on the very severe ones. I believe you acted entirely properly, taking your pets to the emergency clinic. I applaud your decisiveness and presence of mind in this experience. Bruce Williams, DVM Department of Veterinary Pathology [log in to unmask] Armed Forces Institute of Pathology (202) 576-2453/2454 Washington, D.C. 20306-6000 [Posted in FML issue 0847]