Non-Adjuvanted Vaccines Protect Cats Against VSS Cancer

Baton Rouge, Louisiana, UNITED STATES

BATON ROUGE, La., Aug. 28, 2016 (GLOBE NEWSWIRE) -- Injections may be more dangerous for cats than for dogs. This may be because some pet vaccines and drugs contain substances called adjuvants to make them more effective. Adjuvants may be chemicals, parts of microbes or mammalian proteins that may overly irritate a cat's body, reports Jefferson Animal Hospital.

Adjuvants are safe for dogs, people and other pet species, according to Dr. Frederick Michaelson of Baton Rouge's Jefferson Animal Hospital, 8774 Jefferson Highway. However, he stresses that injections containing adjuvants may be the cause of a type of malignant tumor called "vaccine site sarcoma" (VSS).

Types of Feline Vaccines

Vaccines containing small amounts of live viruses are among the most powerful in causing the immune system to create virus-battling antibodies. The immune system also modifies cells to aid in the fight against a virus when exposed to a live form.

Dr. Michaelson notes that his clinic uses the PUREVAX® FeLV vaccine for prevention of feline leukemia. It contains live Canarypox vector, a modified form of bird virus that does not infect mammals yet builds cat immunity to leukemia.

Some forms of live viruses in vaccines can infect pets. To avoid this problem yet protect immune systems, veterinarians often use vaccines that are based on weaker killed or modified viruses. Another modified live-virus vaccine, which Jefferson Animal Hospital uses to prevent feline distemper and respiratory problems, is PUREVAX® Feline 4. It also uses PUREVAX® Feline 4/Rabies, which includes protection against rabies, a form of encephalitis.

Adjuvanted and Non-Adjuvanted Vaccines

Manufacturers boost the power of vaccines containing modified viruses by adding adjuvants, which raise immune response through irritation.

"Out of every 10,000 cats injected with a vaccine containing an adjuvant, about one to two develop cancerous tumors at the injection site," Dr. Michaelson says. He adds that his clinic "only uses the kinds that don't contain adjuvants." It is possible, he notes, that local swelling combined with an adjuvanted injection may lead to VSS.

A pet owner whose cat receives an adjuvanted injection should monitor the injection site for about three months, Dr. Michaelson says. He emphasizes that cat owners should meet with a veterinarian if swelling grows larger than 2 centimeters (a bit more than 0.79 inches) by a month following injection.

Surgical biopsy of a tissue sample from the site of the swelling is necessary to diagnose VSS. Treatment includes surgical removal and radiation or chemotherapy.

Focus on Feline Wellness

Cats have a greater chance of avoiding major viral illnesses if their vaccinations are current, Dr. Michaelson stresses. He adds that vaccinations are part of regularly scheduled wellness visits during which veterinarians can identify any potential health problems and answer questions about pet behavior.

Jefferson Animal Hospital provides services ranging from pet boarding to urgent care. It is open Monday through Saturday and can be contacted on their website at or by calling (225) 927-2344.


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