Vaccination Site Sarcomas in Pets

Vaccination Site Sarcomas are more common in cats than dogs.

One of the hottest and most researched topics in veterinary medicine over the past few decades has been the development of malignant cancers at the sites of previous vaccinations in cats, and to a lesser extent, dogs.  This has especially been a problem with rabies and feline leukemia virus vaccinations.  While there has been much research in this area, no single vaccine manufacturer has been incriminated.

Incidence of this disease is estimated to be between one out of 5,000 pets vaccinated.  It is suspected that the adjuvants (chemicals used for preservatives, and vaccine cultures) in the vaccination may lead to chronic skin inflammation and the development of a malignant sarcoma months to years later.  These cancers may be very difficult to treat, and often require potentially multiple surgeries and/or radiation therapy to try and control.

With the increasing awareness of over-vaccination and its risk to companion animals, it is highly recommended that each pet be looked at as an individual with respect to which, if any, vaccinations are used.  Vaccinations should not be given more frequently than needed, and given only as required by law with respect to rabies vaccination.  Given the innate resistance of adult cats to feline leukemia virus, I don’t recommend using this vaccination in strictly indoor adult cats that are not exposed to other cats.

Any new cats introduced into the household should receive a feline leukemia virus blood test, in lieu of vaccinating for this virus, as the chief method of controlling potential exposure to feline leukemia.  If rabies and feline leukemia virus vaccinations are given, they should be given on separate dates (separated by at least 3 weeks), and as low down on the legs as possible, so that if tumor development occurs, limb amputation may be curative.  Although less common in dogs, vaccination or injection site sarcomas rarely do occur, and treatment with wide surgical resection and biopsy is also recommended.

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