JACK S WEB DIRECTORY FOR VACCINE-ASSOCIATED SARCOMA (VAS)
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Cat Food for Thought:
PLEASE NOTE: This is NOT an
anti-vaccine website, nor am I an anti-vaxxer with respect to human beings. I
fully support getting all recommended vaccines based on scientific evidence,
your health, and your physician s recommendations. I felt that I needed to be
clear on this issue with respect to what is going on in the United States
lately, specifically with the opinions on human vaccinations being expressed by
our Secretary of Health and Human Services, Robert F. Kennedy Jr. This website
is only about vaccines for cats. (Posted October 20, 2025)
THE VAS SCENARIO:
You are a responsible cat owner, and always look after your cat s health. You take your cat to the vet once a year for a checkup and his annual vaccines. Suddenly one day, you feel a small lump on your cat s shoulder. You are not sure what it is, so you keep a watch on it, feeling it every day until you realize that it is not going away in fact, it seems to be growing at an alarming rate. You take your cat to the vet for an examination. You are shocked to find out that your cat has cancer somehow caused by the very vaccinations that you ordered regularly to protect his health. Your cat has Vaccine-Associated Sarcoma, or VAS , something you have never even heard of!
WHAT IS VAS?
Vaccine-Associated Sarcoma, or VAS, is a cancerous, malignant tumor induced by a vaccination. These sarcomas occur in as many as 1 in 1000 cats vaccinated (and probably more because VAS is under-reported). The tumor develops as a consequence of an overzealous inflammatory or immune system reaction to the vaccine.
The VAS tumors develop and grow quickly, are often not responsive to treatment, and result in serious illness and ultimately death of the cat. Recurrence of such tumors is common after surgical removal.
The feline leukemia vaccine and the rabies vaccine are most frequently suspected in pets that develop VAS; however, other kinds of vaccinations may also trigger VAS.
WHAT TO WATCH FOR:
A firm, painless swelling under the skin, in the region of the body in which the cat was vaccinated. Run your hand over your cat s shoulders, back, and rear legs periodically to monitor for development of vaccine-associated sarcomas. If you notice anything, especially 3 months or more after the vaccination, see your veterinarian immediately.
TREATMENT:
Treatment may include one or more of the following: surgical excision, radiation therapy, chemotherapy, and alternative/holistic methods.
PREVENTION:
Talk to your veterinarian about the risk of exposure and the seriousness of VAS when considering any kind of vaccination for your cat. Discuss options for prevention, which may include:
Vaccinating for rabies every 3 years, rather than yearly. If your cat is strictly indoors, consider NOT vaccinating for rabies at all (be aware that some states require rabies vaccination by law).
If your cat is strictly indoors, consider NOT vaccinating for feline leukemia virus.
Insisting on vaccinations being given in the hind quarters (right and left rear legs), or better yet, in the tail. If VAS should develop in these cases, the affected limb (or tail) can be amputated to save the life of the cat. Never allow a vaccination in the scruff or between the shoulder blades!
Keep detailed records for all your cat s vaccinations. These records, provided by the veterinarian administering the vaccine, should include the type of vaccination given, the location of the injection on the cat s body, the manufacturer of the vaccine, and the lot/serial number from the vaccine vial (preferably a sticker that can be placed on your vaccination certificate).
MORE INFORMATION:
For more information, please visit the pages in the menu at the top of this web page. Please note that the links on those pages are by no means meant to be an exhaustive list of links related to VAS. Instead, I have listed the links that I personally have found useful. I will continue to update the list of links whenever I come across something new. I will denote a new link with NEW. In addition, links which are particularly useful will be noted with a .
1. First, learn a little background about VAS by visiting some of the links noted with a on our VAS page.
2. Join the Vaccine Associated Sarcoma Support Group on Yahoo! Groups. With almost 500 members, you will get lots of support from others who are going through the same thing. This group shares lots of information about all stages and treatments of VAS.
3. After your initial shock period has worn off, armed with the new information you have learned and the support of others, decide how to best handle the situation. Remember that even with advice from others, only YOU can decide what is best for you and your cat. Although you don t want to rush to a decision, if you opt for any kind of treatment (alternative or conventional), proceed as quickly as possible, as time is of the essence.
The information contained on this website is intended for general reference purposes only and is not a substitute for professional veterinary advice. Veterinary medical information and treatment standards change rapidly and while we make efforts to obtain the most reliable, up-to-date information, some information may be out-of-date or even unreliable. This information should not be used to diagnose, treat, cure or prevent any disease without the supervision of a licensed veterinarian. Always seek the advice of your veterinarian or other qualified professional.
DEDICATION:
This website is dedicated to the memory of my cat, Jack. At age 9 years old, he succumbed to this horrible disease.
Jack
was first diagnosed with VAS back in June 2002. He had a rapidly
growing tumor in his shoulder area. The VAS came from a
In Memory of Jack
(April 13, 1994 September 5, 2003)
UPDATES SINCE JACK S DEATH:
Adjuvant-Free Vaccines: In 2003, most vaccines contained adjuvants (substances added to boost the immune system's response). These were strongly suspected to cause the chronic inflammation that triggers sarcomas. Today, non-adjuvanted vaccines are widely available and are considered the gold standard by many veterinarians.
Strategic Injection Sites: Back in 2003, vaccines were typically given in the scruff of the neck. Because these tumors are incredibly invasive, removing them from the neck often meant a grim prognosis. Today, the American Animal Hospital Association (AAHA) and veterinary guidelines recommend administering vaccines as low on the legs or in the tail as possible. This allows a surgeon to safely amputate the limb or tail if a tumor does develop, achieving a "clean margin" to save the cat's life.
Any injection can be a trigger: Researchers now understand that it is not necessarily the vaccine itself, but rather the physical trauma of the needle or the inflammatory reaction to any injected substance, that can incite a tumor. Sarcomas have occasionally been linked to microchips, long-acting antibiotics, and even dissolving surgical sutures.
The "3-2-1" Rule: Veterinarians use this quick diagnostic guide for any lump that appears after an injection:
· 3: The lump is still present 3 weeks after the vaccination.
· 2: The lump is larger than 2 centimeters (roughly the size of a marble).
· 1: The lump continues to grow 1 month after the injection.
· If a lump meets any of these criteria, it should be evaluated immediately by a veterinarian.
WHAT ABOUT IBD?
After Jack died, my surviving cat, Sonny, developed IBD. That s Inflammatory Bowel Disease. He had it for over two and one-half years. His symptom was mainly chronic, daily diarrhea and periodic vomiting. After hundreds of dollars of tests, finding nothing, the diagnosis was made. We tried to control it with a change in diet (we had a dramatic improvement at first just by removing all dry food from his diet and replacing it with Fancy Feast wet food that doesn t contain wheat gluten, and later by feeding him 9 Lives Tuna mixed with canned pumpkin) and steroids like Budesonide. Sonny s weight gradually dropped from 11.5 pounds down to 6.5 pounds, and in June 2006, his health deteriorated significantly. Sadly, Sonny died on June 17, 2006.
This website was last updated on: Monday, June 8, 2026