The Irreverent Vet Speaks out on “Are Cat Vaccines Safe?”

The Irreverent Vet Speaks out on “Are Cat Vaccines Safe?”

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Are vaccines safe?

This is a question commonly asked by cat lovers. And it is one that they often struggle with. Cat lovers want to do the right thing, protect their cat but at the same time minimize risk of problems to their cat.

I’d like to address this question. I’m the Irreverent Veterinarian. I give you my opinion and speak the truth regardless of if pet owners or other veterinarians like it or not. I have no hidden agenda here.

So the question that I’ll address in this article is…”Are Vaccines Safe” for your cat?

Are Vaccines Safe?

This is a tough one. The answer is – most vaccines are safe and do way more good than harm. However, there are three types of reactions that can occur from vaccines. The first are mild reactions, the second are allergic reactions and the third is serious reactions that are associated with tumor growth.

  • Mild Reactions – A small percentage of cats will feel a little “sore” after their vaccines. This is the exception rather than the rule. Some cats may run a low-grade fever or just feel a little tired. They may be less active, sleep more and eat slightly less than normal. This is temporary and they generally do fine. It is often hard to tell what of this behavior is from the vaccine or from the stress of going to the clinic to get the vaccine.
  • Allergic Reactions – Some reactions are mild causing itching, swelling, temporary nausea, and others can be serous anaphylactic reactions that are life threatening. To be honest, I’ve never seen a cat die from an allergic reaction to a vaccine. Serious allergic type vaccine reactions in cats are rare.
  • Tumor Associated Reactions – Some cats may develop what is called an “Injection Site Sarcoma“. An injection-site sarcoma, is a tumor thought to be induced by an injection – most often a vaccination. Injection-site sarcomas were first recognized in the late 1980’s when some changes occurred in the vaccine manufacturing process. The actual incidence of injection-site sarcomas is not known with certainty. Some investigators estimate that post-vaccine tumors may occur in as many as 1 of every 1,000 to as few as 1 in every 10,000 cats vaccinated. It is believed that tumors develop week to years after injection.
    This tumor is cancerous and very aggressive. The tumor starts as a small lump but has very small tentacles that extends into the deeper tissues. According to one study, as many as 62 percent of post-vaccinal sarcomas recur within 6 months after surgical removal.

    No one knows for sure why they occur – but it is thought that post-vaccine sarcomas may occur as a consequence of an overzealous inflammatory or immune system reaction to the vaccine. Regardless, they are life-threatening and awful.

My Final Thoughts – Are Vaccines Safe?

This is what I believe. The answer is – most vaccines are safe and do way more good than harm if used properly. I do not recommend OVER-VACCINATING cats. I think that most cats don’t need yearly shots (unless required by law such as Rabies vaccine). I think that each cat should be regarded relative to their risk and ONLY the vaccines that truly protect them should be given.

This brings up the question – what vaccines do cats need? I address exactly this question here – Go to What Vaccines do Cats Really Need.


The Irreverent Vet is a columnist that regularly contributes to The goal is to add a balanced and alternative view of some controversial pet issues. As happens with all of us, veterinarians can’t say what they really think without offending some clients. This commentary allows vets to say what they think and give you, the pet owner, the opportunity to consider another view. All opinions are those of the Politically Incorrect Vet and not the views of and are not endorsed by




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