Veterinarian Column: What are the side effects of dog and cat vaccines?

by Alice's Dog & Cat獣医師

Vaccination against the new coronavirus has begun, and side effects of the vaccine are attracting attention. Every vaccine has side effects. However, the benefits of vaccination are great, so vaccination is carried out. This time we will explain in detail the side effects of vaccines in dogs and cats.

Alice's Dog & Cat Veterinarian Column Dog and Cat Vaccine Adverse Reactions

■Types of side effects of vaccines

・Decrease in activity, fever

This is the most common symptom. It usually subsides within a few days.

・Pain and swelling at the vaccination site

Pain and swelling at the injection site usually subsides within a few days.

・Sarcoma (cat)

Malignant sarcoma may develop in cats at the site of subcutaneous injections of drugs, not just vaccines. It may also metastasize.

Incidence with vaccines: There are reports of 1 to 4 cases per 10,000 vaccinations.

Time of occurrence: 4 months to 3 years after vaccination

Treatment: Surgical removal of the sarcoma. A large excision will be required. Therefore, the vaccination site for cats is the groin of the cat's paw, where it can be completely removed in the event that a sarcoma develops.

If a tumor remains at the vaccination site after vaccination and does not disappear, consult a veterinary hospital.


Skin symptoms: facial swelling, itching, hives, etc. (rare in cats)

Gastrointestinal symptoms: diarrhea, vomiting, etc.

Incidence: In dogs, it has been reported that there are 42.6 cases of skin symptoms per 10,000 doses and 27.9 cases of gastrointestinal symptoms per 10,000 doses.

Period of occurrence: Several hours to 24 hours to several days after vaccination

Treatment: Injection of steroids and anti-allergic drugs, followed by oral administration for several days.


Cardiovascular and respiratory symptoms such as collapse, hypotension, cyanosis, rapid breathing, and difficulty breathing occur. It can be life-threatening if proper treatment is not received.

Incidence: 7.2 cases per 10,000 vaccinations in dogs

Period of occurrence: Within 60 minutes from a few minutes after vaccination. The most common time is within 5 minutes.

Treatment: Provide emergency response. Oxygen inhalation, epinephrine administration, intravenous drip to secure blood vessels, and drugs such as steroids, antihistamines, and bronchodilators are administered.

・Immune-mediated hemolytic anemia, immune-mediated thrombocytopenia

Immune-mediated hemolysis is a disease in which the immune system is involved, destroying red blood cells and causing anemia. Immune-mediated thrombocytopenia is a disease in which the immune system is involved, resulting in platelet destruction and a decrease in platelet count. There are various causes for the onset of the disease, but side effects from vaccination are thought to be one of the causes.

Treatment: Treatment with steroids.

・Other uveitis and encephalitis

Alice's Dog & Cat Veterinarian Column Dog and Cat Vaccine Adverse Reactions

■Precautions during vaccination

-Anaphylaxis often occurs immediately after vaccination. If you develop anaphylaxis, wait in the waiting room for a while to see what happens so that you can receive immediate treatment.

・Skin and gastrointestinal symptoms may appear after returning home. It is dangerous to leave your pet alone after vaccination. Get vaccinated on the day you can see your baby for the whole day.

- Treatment may be delayed in the evening when the veterinary clinic closes immediately after vaccination. Get vaccinated in the morning if possible.

・On the day of vaccination, do not give anything other than medicines that your pet takes every day, such as heartworm medicine. If you experience side effects, you may not know what caused them.

Alice's Dog & Cat Veterinarian Column Dog and Cat Vaccine Adverse Reactions

■If you experience side effects

Symptoms such as feeling a little lethargic may be due to fatigue from going to the veterinary hospital or an immune response from vaccination, and will subside if your dog rests. Anaphylaxis can be life-threatening, so notify veterinary hospital staff immediately. Gastrointestinal symptoms and skin symptoms are also allergies and require treatment. Don't wait to see what's going on and consult a veterinary hospital.

I think many people are worried about what to do with the next vaccine if they experience side effects. If you have an antibody titer that can effectively prevent infection, there is no need to receive vaccines that may cause side effects. In that case, we will perform an antibody titer test. If vaccination is necessary, there are options such as changing from 8 types of vaccines to 6 types of vaccines or changing the manufacturer of the vaccine. Please consult a veterinary hospital.

Vaccines are necessary to protect your beloved pet from serious infectious diseases. Be sure to fully understand the side effects before getting vaccinated.