The answer to this is because the vaccine trial was only ran for one year. Vaccine trials are very expensive and longer trials mean more expense for the company. Over vaccinating can cause health problems too. The new vaccination protocol for dogs and cats is every other or every 3rd year after the initial series and first annual booster. Shouldn't this apply to ferrets too? Any comments from the vets on this matter? Titers can be taken to determine if the animal needs to be vaccinated but from what I've heard it is quite expensive. I haven't checked on the cost myself though. If anyone does do the titer on their ferrets please let all of us know the results and cost. Also, only healthy animals should even be considered for vaccinations. Our vet recommends not vaccinating ferrets with cancer or other ailments and will not vaccinate if they have diarrhea or a cold at that time. Our ferrets have compromised immune systems from severe ECE and no longer receive vaccinations. The youngest of this group is 3 yrs old and all have had the initial series and at least one annual booster. Pre-ECE we vaccinated every other year (my choice and not meant to influence anyone) to avoid compromising the immune system. Each of us must research this issue thoroughly before making our own decision. Weigh the odds as well. Hugs to all. tle [Posted in FML issue 2421]