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Dear Christopher Cat

I have two cats, and I am concerned that they might develop a sarcoma tumor at a vaccination site.
Because they are indoor cats, I am thinking about discontinuing their annual vaccinations. Do you see a problem with this?

Is there an Internet site that will keep me updated on vaccine-associated sarcomas?

Christopher Responds

Yes, and yes.

Cats rarely develop malignant tumors at injection sites. These sarcomas can occur after injection of any medication or vaccine, but they are most often associated with vaccines for feline leukemia and rabies.

The incidence is thought to be in the range of one to ten cats per 10,000 cats vaccinated.

To study the problem and make recommendations, the Vaccine-Associated Feline Sarcoma Task Force was formed through the joint efforts of the American Veterinary Medical Association, the American Association of Feline Practitioners, the Veterinary Cancer Society and the American Animal Hospital Association.

The task force recommends vaccinating cats only for those diseases that really pose a threat, and vaccinating no more frequently than necessary.

Because your cats live indoors, they are unlikely to be exposed to cats with feline leukemia, so the risks of leukemia vaccination probably outweigh the benefits.

On the other hand, it’s a good idea to boost the rabies vaccine every three years. Most people who died of rabies in recent years were unaware that they had been bitten by rabies-infected bats, because most bat bites aren’t painful and don’t leave a mark.

Therefore, if your cat was bitten by a bat, you probably wouldn’t know it.

Vaccinating your cats protects them – and you, if you are exposed to their saliva – from fatal rabies, so it’s easy to understand why rabies vaccination is required by law.

To learn more about other vaccines and to keep updated on the recommendations of the task force, go to

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