Can A Vaccine Give My Cat Cancer?

By Species, By Topic, Cancer, Cats

Over 20 years ago, pathologists began noticing an increase in the diagnosis of malignant tumors that appeared at the site of vaccinations in cats and coined the term Vaccine-Associated Sarcomas. Although this type of tumor had been diagnosed in the past, in the early 1990’s there appeared to be more cases being diagnosed. There were three main events leading up to this period that seemed to have a relationship to the increase discussed below.

The first was the government requirement that all modified-live rabies vaccines were replaced with a killed vaccine. For the immune system to recognize and respond to a killed vaccine, an adjuvant (a substance which enhances the body’s immune response to an antigen) is added to make the vaccine more effective. In addition to the new requirement, there was an outbreak of rabies in wildlife, and subsequently, in pets in the northeast of the United States. This led to several states requiring, for the first time, that all cats become vaccinated against rabies. Also, in the late 1980’s the feline leukemia virus vaccine was also introduced. Like the Rabies vaccine, this was also a killed vaccine-enhanced with an adjuvant.

These three events probably resulted in many cats receiving vaccines for the very first time. They also likely caused many cats that were past due for vaccines to receive a booster. There is an estimate that from 1985-1990 ten times as many cats received vaccinations than in any other 5-year period.

So is this a smoking gun linking vaccines to cancer? Many cat owners thought so. Just like when concerns were raised about adjuvanted human vaccines leading to an increase in autism, the adjuvant—which, remember, is not the vaccine itself, but merely an enhancer—became the initial suspect as a cause for the tumors in cats. Nonetheless, many cat owners blamed vaccines.

The science behind this is a bit more nuanced. For one, it wouldn’t necessarily make sense that the vaccine—if it were capable of causing cancer—would cause cancer in such a localized fashion. So, the initial investigation into adjuvants focused on the inflammation that they cause in order to help the immune system react properly to the vaccine. Researchers thought that may be causing inflammation was also causing the stimulation of tumor growth.

Over the next few decades of intense research, it was noted that many of these tumors were forming at injection sites other than where these vaccines were given. For instance, some tumors occurred at sites where non-adjuvanted vaccines were used. Additionally, injections of antibiotics and steroids were also being linked to tumor formation. As the research progressed, and more information about these tumors became available, it became apparent any injection could stimulate a particular cat into forming a tumor. It seems some cats are genetically predisposed to develop tumors at injection sites. Current epidemiological data suggests that less than 1% of cats have this genetic disposition. Since this apparent genetic predisposition for the tendency to develop tumors is extremely low and it can occur with any type of injection, neglecting vaccinations is not a way of preventing this disease process.

Vaccines provide a great benefit to protecting cats against many deadly diseases, like Rabies, Distemper, Feline Leukemia and Feline Aids. This allows our cats to live longer healthier lives. It also prevents those diseases from spreading to other animals, and in some diseases, to humans.

Also, performing multiple vaccines every three years may put some of these susceptible cats at a greater inflammatory risk compared to performing a single vaccine once-a-year. Unfortunately, this vaccine controversy may have caused thousands of cats to miss their annual wellness examination and, sadly, miss the opportunity for the veterinarian to detect other problems like kidney, heart or thyroid diseases. Early detection and early intervention are important for many of these diseases. Waiting for a cat to show the owner symptoms may, unfortunately, cause the cat unnecessary harm, suffering and a prolonged treatment regime.

Should I vaccinate my cat? The answer is an unequivocal “yes!”

Call CEDARCREST Animal Clinic at 540-943-7577 to discuss which vaccines are appropriate for your cat’s age and lifestyle.

CEDARCREST Animal Clinic provides medical and surgical care for every stage of your pet's life including preventive wellness care exams and vaccines, spays/neuters, and a variety of specialized care for your dog, cat, avian, or exotic. We are home to the only veterinarian practitioner in Virginia to be double Boarded in Avian and Canine/Feline care and provide care for birds, small mammals, and reptiles of all sorts! Plus, we are home to Virginia's most exclusive dog boarding resort that includes heated floors, an expansive play area, and even webcams so you can watch your pet while you're away. We're located in Fishersville, Virginia, and serve Augusta County and surrounding areas including Waynesboro, Staunton, Harrisonburg, and Charlottesville. 

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