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Where your doctor gives you your vaccinations may not have changed much over the years. Nine times out of 10, you are going to feel the needle in either your arm or your derriere. What you may not have noticed is that the same is not true for your cat. Where cats routinely receive vaccinations has changed over the past 10 years. Why? Because of a type of cancer called sarcoma that, although rare, is associated with many injections, including vaccines. It’s one of the main reasons that the veterinary community has invested a lot of time and effort in researching the best place to vaccinate your cat.

Here’s some of the latest news on the issue.

Tail Tweets

Not too long ago, I received a flurry of tweets reporting that according to a recent study, the tail is now where I should be vaccinating my feline patients in order to prevent cancer. As a veterinary oncologist, I have, unfortunately, cared for a number of cats suffering from injection-site sarcomas and would prefer to never see one of those tumors again. Because vaccines are a common type of injection administered to cats, they may in some patients be one of several inciting factors for an injection-site sarcoma.

Current Practice

To investigate the news, I turned to the most recent cat vaccination guidelines. The American Association of Feline Practitioners (AAFP) periodically releases vaccination recommendations from its Feline Vaccination Advisory Panel (FVAP), a group of experts in feline infectious disease and vaccinology. The most recent guidelines were published in September 2013 — fairly recently — and the authors outlined specific locations for the administration of vaccines. Their report included photographs of recommended administration sites that were widely published within the veterinary community.

Oncology Viewpoint

As a veterinary oncologist, I know that the advisory panel chose the recommended vaccination sites with the management of injection-site sarcomas in mind. If vaccines are administered in a front or hind leg and result in a sarcoma, the tumors can be removed with limb amputation. From my specialist’s viewpoint, tumors occurring as a result of vaccination in the hip, shoulder or chest area — the areas not recommended by the guidelines — are very difficult to remove. Successful treatment of those tumors also usually requires radiation therapy and chemotherapy in addition to surgery.

At first glance, from an oncologist’s viewpoint, vaccinating in the tail makes sense. While no one wants to see his favorite kitty lose any body part, the loss of the tail compared to a limb is minimally debilitating and only mildly painful. A tail amputation seems far better and simpler, in my mind, than amputating a leg. So if people are tweeting about using the tail as a vaccination site, why didn’t the advisory panel include it in its recommendations? A bit of reading in Journal of Feline Medicine and Surgery provided the answer.

Pilot Results vs. Protocol

The impetus for a lot of my “tail tweets" was an article that first appeared in October in the journal’s online edition and later in its April print edition. The article, titled "Tail Vaccination in Cats: A Pilot Study," proposed the use of the tail as a possible vaccination site and was widely reported. However, it’s important to realize that a pilot study is by no means a definitive scientific exploration. The study surveyed 94 veterinary oncologists about their experiences with 60 cats.

Pilot studies are very useful because they can raise interesting questions and ideas for practitioners and researchers to consider. But they often are given wide coverage in mainstream media in a way that makes them seem much more authoritative than they really are. In reality, pilot studies are just the beginning step in looking at whether a practice is medically sound. A pilot study does not analyze safety or efficacy.

Because the tail vaccination research was only a pilot study, in my book, it does not contain enough information to change feline vaccination protocol — yet. However, it does raise an interesting idea. Hopefully, a funding agency will see the importance of a larger-scale clinical trial that looks at the safety, efficacy and validity of tail vaccination in cats and will fund a trial that includes enough cats to make a strong and definitive scientific recommendation. From a patient stress standpoint, the pilot study also showed that slightly more cats had minimal to no reaction to tail vaccination compared to vaccination in the hind leg, but more study is needed to confirm that finding.

We need to keep in mind that even though the data in the pilot study about tail vaccination was encouraging, larger studies do not always draw the same conclusion as a pilot study. At a time when many researchers and scientists are looking ever more critically at the conclusions drawn by even major studies, I think caution is called for.

So for now, following existing guidelines would seem to be the best approach. Veterinarians and cat owners alike will wait and hope for scientifically confirmed news about whether the tail is a better vaccination site that can still offer adequate vaccine protection to our cats against infectious disease while helping to prevent cancer. Until then, I, for one, plan to continue following the existing protocol.

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