Any treatment carries some risk, but these risks should be weighed against the benefits of protecting your pet from potentially fatal diseases. Most pets respond well to vaccines. The most common adverse responses are mild and short-term, including fever, sluggishness, and reduced appetite. Pets may also experience temporary pain or subtle swelling at the site of vaccination. Although most adverse reactions will resolve within a day or two, any excessive or continued pain, swelling or listlessness should be discussed with your veterinarian.

Rarely, more serious adverse reactions can occur. Allergic reactions appear within minutes or hours of a vaccination and may include repeated vomiting or diarrhea, whole body itching, swelling of the face or legs, difficulty breathing or collapse. Contact your veterinarian immediately if any of these symptoms are seen. In very rare instances, death could occur from an allergic reaction. There are other uncommon but serious adverse reactions, including injection site tumors (sarcomas) in cats, which can develop weeks or months after a vaccination. The best advice is to always tell your veterinarian about any abnormalities you notice after your pet has been vaccinated.