Lump Under Cat’s Skin After Vaccination


Causes of lump after vaccination   What should you do?   Other side effects of vaccinations   Vaccination protocol   Annual vs tri-annual vaccinations

Lump under cat

Causes of lump under the skin after a vaccination:

Vaccinations are a necessary part of pet ownership and have saved countless lives. But like any medical treatment, they do come with their risks. A common question that cat owners ask is:

Is it normal for a cat to develop a lump under the skin after a vaccination?

The short answer is yes, a small (pea sized), mobile, firm, painless lump at the injection site can occur.  This is caused by a granuloma, which is a collection of immune cells. Most of the time, this lump will go away within a few weeks. Warm compresses can help to resolve these lumps.

However, a far more serious side effect is a vaccine-associated sarcoma (VAS), which is a rare but very aggressive type of cancer of the connective and soft tissues. It is most commonly associated with rabies and feline leukemia vaccines. The incidence is between 1 – 1,000 to 1 – 10,000 cats.

What should you do if you notice a lump under your cat’s skin:

Keep a close eye on it. If the lump hasn’t disappeared within a month or if the lump grows larger, seek veterinary attention.

A biopsy for laboratory evaluation will be performed to determine the cause.

Other side effects of vaccination:

Typically side effects are self-limiting but may include general malaise, loss of appetite, low-grade fever, sneezing and pain at the site of the injection.  These usually only last a day or so. If symptoms persist, please take your cat back to the veterinarian.

Vaccine protocol:

The Vaccine Associated Feline Sarcoma Taskforce now recommends that veterinarians now administer vaccinations in different locations on your cat’s body. Current protocols are:

  • Rabies – Right rear leg
  • Feline leukemia – Left rear leg
  • FRVCP (F3) – Shoulder

Amputation of the limb can be performed in the event that a cat develops VAS.

Annual boosters vs tri-annual boosters:

A great number of veterinarians are switching away from the annual booster in preference of booster shots every three years, for low-risk cats. Speak to your own veterinarian as they know your cat, his medical history and the incidence of diseases in your area.

Many councils require an annual rabies vaccine, and you must comply with these regulations. The feline leukemia vaccine should only be given if your cat is at risk, such as if he is allowed outdoors.

Please remember that vaccines have done far more good than harm. Being aware of any lumps and bumps, following your veterinarian’s vaccine protocol and seeking medical attention quickly is the best course of action.

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