If your cat develops a bump after vaccination, it will usually subside on its own. If your cat remains healthy and the bump doesn't change much or even gradually shrinks and disappears, there's no need to worry; just let it disappear on its own. However, if the bump becomes very large in the first week after vaccination, especially if it turns red and is painful, or if your pet shows signs of illness, you must take it to the vet immediately.
A bulge or bacterial infection may appear on a cat after vaccination.
Not all injection site bulges are typical vaccine reactions: if a bacterial infection occurred during vaccination, or if bacteria entered the skin through the needle puncture site after injection, a local abscess may occur.
The cat has a bump or inflammatory reaction after getting vaccinated.If a lump doesn't change size significantly in the first few years but then suddenly and inexplicably starts to grow larger, we strongly recommend that you take your pet to the vet for a checkup as soon as possible. This could be an inflammatory reaction caused by cancer (such as feline vaccine-associated sarcoma) or a vaccine-induced inflammatory reaction. If this is the cause, you'll need to make it a habit to regularly check your pet's skin and observe any lumps or bumps. If there are any changes, seek veterinary attention immediately.
