Adverse Vaccine Reactions in Pets

Other topics
Husky puppy getting a shot

Veterinarians use vaccines to protect pets from serious diseases. In the majority of cases, pets receive vaccines with no ill effects. Among those who do respond badly in some way, the majority of the adverse vaccine reactions are not life threatening.

However, if you notice any changes in your pet’s health following a vaccination, call your veterinarian immediately.

If a pet develops a pattern of adverse vaccine reactions, it may indicate the pet is at higher risk of something more serious happening following future vaccinations. Share all of your concerns about vaccines with your veterinarian so that you can collaborate on a vaccine plan that makes sense for your pet.

Common Adverse Vaccine Reactions

  • Vomiting

  • Facial swelling

  • Injection site swelling or lump

  • Lethargy (being unusually tired)

  • Hives

  • Shock (which can be serious)

  • Injection site pain

  • Itching

  • Injection site hair loss

  • Diarrhea

Less Common Adverse Vaccine Reactions

  • Not eating

  • Fever

  • Dangerous allergic reaction and shock (anaphylaxis)

  • Trouble walking or standing (ataxia and other signs of neurological problems)

  • Lameness

  • General signs of pain

  • Hyperactivity

  • Muscle tremors

  • Heart rhythm problems (tachycardia)

  • Low platelet count (thrombocytopenia)

  • Autoimmune disorders

  • Death

Affected Breeds

Any individual pet may be susceptible, but smaller dogs tend to experience more adverse vaccine reactions:


The risks for adverse vaccine reactions go up based on a few known factors:

  • Less a dog weighs

  • More vaccines given at once

  • Kind of vaccines given, with rabies and Borrelia (Lyme disease) posing the highest number of adverse events

  • Number of booster vaccines given over a pet’s life (Some dogs have no trouble until the third or fourth injection of the same vaccine.)

Discuss your pet’s vaccine needs and timing with your veterinarian, including the options to:

  • Follow modern vaccine booster protocols rather than giving every vaccine every year

  • Use titer testing (blood tests looking for antibodies) to determine a pet’s immunity to a specific disease

  • Give only one vaccine at a time

  • Skip certain vaccines based on your pet’s medical history and age


Veterinary treatment greatly depends on the symptoms and seriousness of a pet’s adverse vaccine reaction. Veterinarians may administer antihistamines and steroids to treat many common reactions.

Serious adverse vaccine reactions require emergency intervention, hospitalization, and sometimes life-long management.

How to Report an Adverse Vaccine Reaction

The United States Department of Agriculture (USDA) oversees veterinary vaccines through its Center for Veterinary Biologics.

Reporting of adverse vaccine reactions is voluntary. Usually, veterinarians file adverse vaccine reaction reports on your behalf. If you choose to do so yourself, here is what’s required.

Vaccine Maker: First, contact the vaccine’s manufacturer, through its veterinary services or technical services department. Visit the company’s main website and look for a toll-free phone number for that department. Have the following information ready before you call:

  • Your pet’s breed, age, health status at the time of vaccination

  • Date of vaccination

  • Number and type of vaccinations given, including lot numbers for the vaccine(s)

  • Description of your pet’s symptoms

  • How soon after vaccination the symptoms began

  • Your pet’s outcome or prognosis (if known)

USDA: Once you’ve alerted the vaccine’s manufacturer, then you can also contact the USDA.

Online: USDA – Center for Veterinary Biologics

By Phone: (800) 752-6255

By Fax: (515) 337-6120

By Mail: Center for Veterinary Biologics, 1920 Dayton Avenue, P.O. Box 844 Ames, Iowa 50010


Adverse events diagnosed within three days of vaccine administration in dogs, JAVMA, Vol 227, No 7, October 1, 2005.

Postmarketing surveillance of rabies vaccines for dogs to evaluate safety and efficacy, JAVMA, Vol 232, No 7, April 1, 2008.