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Tail Vaccinations May Facilitate Cancer Treatment in Cats (Study Explained)

Written by: Ingrid King

Last Updated on January 6, 2024 by Catster Editorial Team


Tail Vaccinations May Facilitate Cancer Treatment in Cats (Study Explained)

When administering vaccinations to cats, most veterinarians give the injections below the elbow or knee joint in the leg, as recommended by the American Association of Feline Practitioners most recent guidelines. However, a recent study suggests that the tip of a cat’s tail appears to be as effective as vaccines at traditional sites.


Why inject vaccines into the tail?

The study was motivated by the high incidence of vaccine-induced sarcomas in cats. The incidence of these tumors ranges from 1 in 1000 to 1 in 10,000 cats. They can develop as quickly as 4 weeks or as late as 10 years post vaccination.

Typical treatment of these tumors is aggressive surgery. Since these tumors often infiltrate surrounding tissue, surgeons need to excise the tumor with a wide margin. This frequently means that the leg will need to be amputated. As a result, many cat guardians don’t pursue treatment, since this kind of extensive surgery is disfiguring, painful, and often very expensive. Injection into the tip of the tail would reduce the trauma of live saving surgery for cats who develop vaccine-induced cancers.

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The study

Sixty cats were enrolled in the study. Thirty-one received vaccines in a hind leg below the knee and 20 received the same vaccines toward the back end of the tail. The researchers used a six-point scale (1 = no reaction, 6 = injection not possible) to assess the way in which the cats reacted to being vaccinated. They found “no significant differences” in the cats’ reactions to receiving injections in the tail versus the leg.

The researchers also collected blood samples from the cats to ensure that tail vaccination stimulated a good immune response.

Veterinarian doctors analyzing blood samples of cat in laboratory under microscope
Image Credit: Kzenon, Shutterstock

What does it mean for your cat?

While some vets may begin tail vaccinations, it is doubtful that the veterinary community as a whole will jump on this bandwagon immediately. The study was only a pilot study and not a new recommendation for vaccine sites, as much of the media coverage would suggest.

The best vaccine plan for your cat will result from a thorough discussion with your veterinarian, taking your cat’s lifestyle and history into account, and assessing the the risks and benefits of vaccination, so you can make an informed choice for your cat.

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The bigger picture

Veterinarians should be far more concerned about the high incidence of these cancers, than about the injection site itself. While vaccinations protect against disease, the emphasis should be put on avoiding adjuvanted vaccines. Adjuvants are substances added to a vaccine to enhance the immune system’s reaction, and studies suggest that they are responsible for the formation of tumors.

Reducing the frequency of vaccinations, and recommending titer testing as an alternative, should also be considered. Studies conducted at the University of Wisconsin School of Veterinary Medicine have shown that immunity for some vaccines last seven years or longer, which suggests that even the more conservative vaccine protocols recommended by major veterinary organizations are still too frequent.

At this point, there are a lot of unanswered questions. Not enough cats have been vaccinated in the tail to really know whether this will truly reduce the incidence of injection-site sarcomas, and additionally, these cancers can take years to develop. But if your cat’s veterinarian starts vaccinating your cat in her tail, you will know why.

This article was previously published on and is republished with permission.

Featured Image Credit: Tyler Olson, Shutterstock

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