Dog Vaccination Concerns: Vaccinating Your Dog and Potential Side Effects

Does your dog need to be vaccinated? Are you pro vaccinations or do you refuse to consider them?

In the past, dogs routinely received vaccination against just about anything we could think of. The reasoning was the off-chance of exposure, in which case the vaccine should protect the dog.

Today, we recognize that vaccines can have a downside as well. 

Dog Vaccination Concerns: Vaccinating Your Dog and Potential Side Effects

Common vaccination side effects

There can be side effects with any medication, and vaccines are no exception.

Anaphylactic/Allergic Reactions

By far, the most common adverse reaction to vaccinations in dogs is an allergic reaction.

  • A normal reaction to vaccines includes mild lethargy and soreness. A mild fever may also occur and these symptoms are generally not serious.
  • Vaccine reactions can occur directly after the administration of a vaccine or within 48 hours later.
  • Hives, swelling of the face, muzzle and ears and sometimes nausea—associated with an allergic reaction.
  • In more severe cases, the dog may go into shock and may also die suddenly. Fortunately, this complication is extremely rare.

Which dogs are most likely to have adverse reactions to vaccines?

Puppies and young dogs are most likely to suffer adverse reactions to vaccination. In addition, small breeds of dogs are at higher risk than larger breeds.

Administering multiple vaccinations simultaneously is more likely to elicit an adverse reaction.

Interestingly, multi-valent vaccines—more than one antigen in one shot—do not appear to increase the incidence of adverse reactions.

Immune-mediated disease linked to vaccines

At this time, the link between immune-mediated disease and vaccinations is unclear. However, there is some evidence that vaccinations can at least predispose a dog to develop an immune-mediated disease.

We need more research. But there is a concern that vaccination could have a long-term effect on the immune system. That makes it necessary to minimize unnecessary vaccinations.

Vaccine preservatives, mercury, and thimerosal

Some vaccinations contain various preservatives, including mercury and thimerosal (a compound containing 49.6% mercury by weight).

The addition of preservatives prevents the growth of micro-organisms—such as bacteria or fungi—in the event of accidental contamination. However, not all vaccines contain mercury or thimerosal.

There have been concerns about the safety of mercury and thimerosal in vaccinations in human medicine.

The belief was that these substances might correlate to the development of autism or another neurodevelopmental disease. However, studies investigating this causal relationship have failed to prove a positive correlation. According to the FDA publication Questions About Vaccines. Similar animal studies have also failed to show a link between adverse reactions and mercury or thimerosal content.

This continues to be a controversial and widely debated topic, however.


Adjuvants are substances that increase the body’s response to the vaccine. That leads to better protection with smaller quantities of the biological portion of the vaccine.

However, adjuvants have been implicated in causing cancer in dogs. 

This is another reason that unnecessary vaccination should be eliminated from the vaccination protocol for individual animals.

Some vaccinations are free of adjuvants, and many veterinarians consider these safer than adjuvanted vaccines.

Why vaccinate?

Why administer vaccines to dogs and cats with the risks involved?

Despite the risks involved, vaccines still provide documented benefits which in most cases outweigh any risks involved with their administration.

However, vaccines protocols for an individual animal must assess the relative risk for the individual. Only choose vaccines that have the potential for more benefit than risk.

Core versus noncore vaccinations

Core vaccinations are those that all dogs need. They protect against deadly diseases with no treatment and include:

  • Rabies
  • Parvovirus
  • Distemper
  • Parainfluenza

Non-core vaccines are those that your dog may or may not need depending on their environment, lifestyle, and overall health and include:

  • Kennel cough
  • Leptospirosis
  • Lyme disease
  • Influenza
  • Rattlesnake

Further information: Vaccination recommendations for general practice

Related articles:
Dog Health and Vaccines: Problems With Canine Over-Vaccination

Further reading:
Dog Health and Vaccines: Problems With Canine Over-Vaccination
To Vaccinate or Not: A Vet’s Perspective
Vaccinosis in Dogs: A Vexing Conundrum. Can Physical Therapy Help?
To Booster or not to Booster

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