Merial, Ltd. has released a new rabies vaccine for cats, apparently in response to veterinarian and owner concerns about the safety of added adjuvants, substances that are intended to increase the immune response mounted by a cat after receiving a vaccine. The new formulation, used in their line of PUREVAX® vaccines, purports to provide protection from the rabies virus for three years without the help of adjuvants that were used in earlier formulations of the vaccine.

Adjuvants have been the source of significant controversy since they were implicated as a potential cause of feline injection-site sarcomas (FISS), a type of cancer that may occur at the site of injections in cats. Although the relationship between adjuvants and FISS remains the subject of ongoing debate and research, it seems prudent to avoid the use of adjuvants in feline vaccines, provided that these new non-adjuvanted vaccines offer protection that is comparable to similar vaccines formulated with adjuvants. Until now, non-adjuvanted rabies vaccines for cats only provided one-year protection from rabies infection.

We recommend that you discuss this new vaccine option with your veterinarian and fully understand your options.