Lump Under Cat’s Skin After Vaccination

Lump under cat

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 if it is 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.

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

Keep a close eye on it. If the lump hasn’t disappeared within a month or if the lump grows larger, seek veterinary attention. Your veterinarian will perform a biopsy of the lump which will be sent to a laboratory for evaluation.

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 – Shoulder.

So, should the worst occur and your cat develops a VAS, the affected limb can be amputated?

Annual boosters:

A great number of veterinarians are switching away from the annual booster in preference of booster shots every three years, to reduce the incidence of VAS.

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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