Vaccine-Associated Sarcoma In Cats

Some cats (existing data reflects a number somewhere between 1 in 2,000 and 1 in 10,000) show an increased potential to develop malignant skin tumors at sites on their bodies where vaccines are administered. These tumors are extremely aggressive, have a very high likelihood of regrowth after conservative surgery, and an unpredictable rate of spread. The prognosis is normally not optimistic in cats that present with them.

These tumors are a form of cancer called "Sarcoma". Most feline sarcomas are not associated with vaccines in any way, but those that are associated have both pet owners and veterinarians alike deeply concerned. When they occur at a site where vaccines are administered, they are referred to as "Vaccine-Associated Feline Sarcoma". We have seen these types of tumors infrequently in cats for a long while now, but as recently as 1991, we began to see a much higher incidence of these sarcomas occurring in the very places where vaccines are commonly injected. The association between vaccine administration and sarcoma development is firmly documented.

Even though vaccine-associated sarcomas are relatively uncommon, national veterinary organizations as well as feline vaccine manufacturers felt it was important enough of an issue to organize the Vaccine-Associated Feline Sarcoma Task Force, a coalition of Veterinarians, Vaccine Manufacturers, and other Feline Health Care practitioners dedicated to resolving the dilemma. This task force is devoting considerable human and financial resources to determine the true scope of the problem, the cause, and the most effective treatment of vaccine-associated sarcomas.

As concerning as this issue may be, there is an even greater concern that many cat owners, in an attempt to keep their cats from developing Vaccine-Associated Sarcoma, may choose to stop allowing all vaccinations entirely. While this response may be well intentioned, the sad result is that these owners may be placing their cats at a much higher risk of acquiring a fatal infection than any risk the vaccine poses. In many locations, there are ordinances and other legal requirements regarding compliance with rabies vaccine protocols. You will need to check with your vet or local officials to see if the Rabies vaccine is required for cats where you live.

It is up to us to determine what is the best course of action for our pets. The best suggestion is to learn as much as you can about Vaccine-Associated Sarcoma, discuss the issue at length with your trusted veterinarian and as a team, reach a treatment plan best suited for you and for your cat. Veterinarians and pet owners are being urged to identify and closely evaluate each individual cat's risk of exposure as a guide in deciding which vaccines should be given. After considering both the vaccine and your cat's individual circumstances, your veterinarian will assist you in designing a vaccination program that not only protects against infectious disease but is also as safe for your cat as possible.

The choice of which vaccines your cat should receive can be appropriately made by closely examining the following factors:

1. Evaluate your cat's exposure to other cats. Your cat's risk of acquiring the common feline infections and viruses is largely dependent on the health/medical history of any other cats to which he/she is exposed. Advise your vet whether your cat goes outside or has contact with any other animals. Provide a list of all of your other pets, whether or not their vaccines are up-to-date and whether or not they have access to the outside or other animals.
2. The risk an infected cat poses to human health. Most of the common feline infectious health problems cannot be transferred to humans. One exception to this is the Rabies Virus, which can be acquired by humans.
3. The protective ability of the vaccine. Some vaccines provide very little, if any protection and others are not always indicated for indoor-only cats.
4. The frequency or severity of reactions the vaccine produces. Many feline vaccines may cause reactions ranging from nothing at all to severe and in rare cases, fatal. These reactions should be carefully considered before making the decision to vaccinate. It is normal to observe a slight or mild reaction in otherwise healthy cats after receiving vaccines. You will need to discuss with your vet at what time would it be considered severe and how to contact someone for help if you need it.
5. The age and health status of your cat. Advise your vet of your cat's age (or closest guess if your don't know for certain) as well as detailed health history. It is helpful to keep an organized journal of all of your cat's visits to the vet, including an itemized statement of services rendered and provide that whenever a plan of treatment needs to be discussed.
6. Vaccine reactions your cat may have experienced in the past. It is important to let your vet know if your cat has ever experienced a reaction to a vaccine and the details of that reaction. If the reaction was severe, your vet may decide not to vaccinate at all.

It needs to be emphasized that in the vast majority of situations, vaccines are much more beneficial than harmful and they continue to help protect cats from serious infection and disease. Unless there is a sound medical reason to avoid vaccines, all cats should be correctly assessed for potential risks to the common feline infections and viruses and vaccinated accordingly.

You can minimize the risk of Vaccine-Associated Sarcoma in your own cats by not vaccinating unnecessarily. Keep meticulous records of your pet's vaccination schedule, including date, administering Vet's name and current contact info, type/brand of vaccine, amount administered, and location on the body where administered. Do NOT leave your vet's office without such a document in your hand if your cat received ANY injections. You should have a detailed, written listing of all injections, not just vaccines. According to recent research, in cats presenting a genetic predisposition to Vaccine-Associated Sarcoma, tumors have developed in sites where only sterile water or fluids were administered.