Feline Vaccine-Associated Sarcomas: Historical Review & Current Recommendations

Feline vaccine-associated sarcomas were initially recognized in the late 1980’s. An increase in fibrosarcomas was noticed in the pathology Lab-oratory of Pathology at the University of Pennsyl-vania School of Veterinary Medicine. This in-crease coincided with the implementation of a mandatory feline rabies vaccination law. The sar-comas had similar histologic features to injection site inflammatory reactions. Later research re-vealed aluminum, a common vaccine adjuvant, within the cytoplasm of tumor macrophages. This increased suspicion that vaccine was more than just circumstantially involved. A letter to the editor1 of the Journal of the Ameri-can Veterinary Medical Association (JAVMA) in 1991