Safety Through Science

Vaccines have really started to become high-tech, and we're taking advantage of it. The international pharmaceutical giant, Merial, has used recombinant DNA technology to develop vaccines for cats that eliminate the need for adjuvants. Adjuvants are substances that are added to vaccines to enhance the patient's immune response to the vaccine. Unfortunately, they are also implicated in local reactions to vaccines and, in rare instances, tumors called vaccine-associated sarcomas.

Vaccine-associated sarcomas reportedly develop in 1-5 cats out of 10,000 vaccinated. Only certain genetically predisposed cats seem to be affected, but there is no current means of determining which cats belong to this unfortunate group. Rabies and Feline Leukemia are the two vaccines most often associated with the problem, because most of the currently available vaccines for these two diseases contain an adjuvant. Merial has developed recombinant DNA vaccines for both diseases, allowing us to completely eliminate the use of adjuvants in cats (the "Feline Distemper" vaccine is a modified-live vaccine and does not contain adjuvant).

These newer vaccines are more expensive than the older adjuvanted ones, but we feel they are worth it. We still carry the adjuvanted rabies vaccine for clients that are on a restricted budget and are willing to take the small risk associated with that vaccine. The recombinant rabies vaccine is currently approved for annual vaccination rather than the three year duration of the adjuvanted vaccines, but our feline patients need to be examined annually anyway.

The recombinant Feline Leukemia vaccine is particularly interesting. It is administered with an air syringe! No needle is involved. A tiny volume of vaccine is injected just under the surface of the skin by a blast of high-pressure air. We hold the syringe against kitty's leg, there is a loud click, and the vaccination is complete.

Let us know if you have any questions about these new vaccines. We're happy to discuss them.

Steve McBride, DVM