Side effects of canine annual vaccines

Updated April 17, 2017

Vaccines are an important aspect in keeping your dog as healthy as possible; however, they do come with the potential for side effects. The side effects are generally mild and the risks your dog faces if not vaccinated are more harmful than the potential side effects it may encounter from the vaccines. Side effects can affect any breed or age of dog; however, there are a few dogs who are more at risk for the side effects, as there are certain vaccines that have a higher incidence of causing reactions.


According to Pet-Informed, one of the most common vaccine side effects is lethargy. Most dogs and puppies will sleep more and not want to move around as much for about 24 hours after a vaccine is administered. This is because most vaccines contain live viruses and the bodywork hard to try to fight them, similar to when the body is trying to rid itself of an illness. As a dog becomes older and receives more of the shots, this type of side effect may occur less frequently. Puppies that are receiving the vaccines for the first time are more likely to experience this side effect. If the lethargy is severe or lasts longer than one day, contact your veterinarian.

Decreased Appetite

A puppy or dog may avoid food for about 24 hours after it has received a vaccination. This generally occurs because the dog doesn't feel well as a result of the vaccine. Just like with humans, if we feel sick, it is likely that we are not going to want to eat a big meal. If the dog or puppy continues to avoid eating after 24 hours, consult a veterinarian.

Bump or Swelling at Injection Site

It is common for a dog to have a pea- to marble-sized bump where the injection was administered, particularly if the vaccine is of the killed variety and contains reactive adjuvants. The bumps are usually a combination of inflammatory cells and scar tissue. The bumps may disappear, reduce in size or become permanent. Hair loss and skin colour change may also occur at the injection site.

Anaphylactic Shock

While not common, anaphylactic shock is extremely dangerous and can occur after a vaccine is given. According to, dogs that experience this rare side effect will have a sudden onset of diarrhoea, vomiting, seizures, coma, facial swelling or death. This type of reaction can occur within minutes of receiving the vaccine and up to 24 hours after. Dogs that experience these symptoms should be rushed to a veterinarian for shock treatment.

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