What Happens If A Dog Gets Vaccinated Twice?

One of the primary responsibilities of any dog owner is to ensure that all required vaccinations are made promptly and appropriately. Unfortunately, sometimes due to an accident or mistake by the owner or veterinarian, or due to other circumstances, the dog may get two jabs instead of one or get another vaccination while the previous one is still active.

So, what happens if a dog gets vaccinated twice?

Here is what you need to know about the possible side effects of your pup getting over-vaccinated, as well as ways to prevent it in the future.

What Happens If A Dog Gets Vaccinated Twice?

A second unnecessary vaccination may not cause any immediate side effects on a dog, but over-vaccination should be prevented whenever possible. Vaccinating a dog with the same vaccine twice in a row can cause some mild to severe adverse reactions, including autoimmune diseases, allergic reactions, changes in behavior and, unfortunately, in some cases, death.

To prevent such dangerous side effects, dog owners should be cautious when rescheduling the vaccination of their pups. Understanding what can happen due to over-vaccination can help take the necessary precautions to avoid such incidents.

Here are the potential adverse reactions to vaccinating your dog:

Allergic Reactions

According to studies, younger adult small breed dogs are at a greater risk of a negative reaction from being vaccinated in the first three days after the vaccination.

This, though, is not the case when multivalent vaccines for parainfluenza, parvovirus, kennel cough, or bordetella are administered.

While most of the initial allergic reactions following vaccination will disappear in a couple of days, there are some cases of more severe allergic reactions, including:

  • Pain, swelling, and redness at the injection site can appear. The area where the injection was made can also develop an abscess and collect pus after the vaccination. In some cases, sarcoma can develop at the injection site and lead to cancer development.
  • Breathing problems. Some intranasal vaccines can cause mild coughing, sneezing, and nose discharge in some dogs.
  • There can be a decrease or loss of appetite, which usually occurs in the first two days following the vaccination. It is often accompanied by depression and a mild fever
  • This is a severe allergic reaction that requires emergency treatment. Symptoms of this rare but dangerous allergic reaction include sudden diarrhea, vomiting, a fast but weak pulse, seizures, drowsiness, swelling of the face, and other worrying symptoms. It can be a life-threatening condition that can cause respiratory or cardiac failure and death.

An Overload Of The Immune System

The immune system of canines consists of two main classes – the cellular immune system and the humoral immunity.

The cellular immune class is the primary immune defense system of a dog. Humoral immunity is the system that provides secondary defense and is responsible for producing antigen antibodies.

If one of these classes becomes predominant, the vaccine can bypass the main immune system and activate the humoral system. This makes the humoral system dominant over the central defense system, which causes a reversal in the dog’s natural defense and can cause an autoimmune reaction and disease by turning the immune system against itself.

Changes In The Behavior

Vaccines contain an actual virus that causes an immune reaction and an immune adjuvant that boosts this response from the immune system.

The adjuvants in vaccines can contain highly toxic substances, including aluminum, mercury, or MSG. In cases where these adjuvants stimulate a prolonged activation, this can cause inflammation of the dog’s brain, often leading to behavioral changes.

With over-immunization, in some cases, the dog can become aggressive to animals and people. Other behavioral changes from over-immunizing a dog can include:

  • Hypersensitivity
  • Coughing, choking, or gagging when eating
  • Rage, aggression, agitation, and violent behavior
  • Unexplained fear and suspicion
  • Extreme fear or desire for water
  • Abnormally high sexual drive and focal licking
  • Constant and unwarranted erections
  • Obsessive-compulsive biting and chasing
  • Sensitivity to small spaces, tight clothes, or noise
  • Accidental urination
  • Purposeless vocalization or wandering

Useful Tips For The Prevention Of Over-Vaccinating Your Dog


Vaccines are essential for dogs, but when they are administered properly and according to schedule.

Dog parents can prevent over-vaccination or adverse reactions to vaccines by getting familiarized with the basics of vaccinations, keeping an eye for the possible adverse reactions, resorting to titer tests, and keeping and sticking to a vaccination schedule for the pup.

Here are some useful tips for owners on how to prevent over-vaccination of their dogs:

Learn More About The Different Vaccines

Some vaccines are known as core vaccines and are crucial for protecting puppies and dogs from life-threatening diseases, such as canine parvovirus, canine distemper, and canine adenovirus. These core vaccines are administered when the puppy is 8 to 16 weeks of age.

Another obligatory core vaccine is the rabies vaccine since rabies cannot be cured and is 100% fatal. But the dog will receive the rabies vaccine only once, preferably between the ages of 12 to 16 weeks.

According to your veterinarian’s vaccine schedule, boosters are required for the core vaccines.

Along with the essential core vaccines, your dog may require specific non-core vaccines for bordetella, parainfluenza, Borrelia burgdorferi, Lyme disease, canine influenza, and leptospirosis, depending on the area you live in, your lifestyle, the local environment, and the risk of contracting any of these diseases.

You must speak to your veterinarian, request a vaccination schedule for your dog, and follow it strictly.

Record Your Dog’s Vaccinations

While your veterinarian will log all vaccinations and other medical records of your dog on a doctor’s card, the prevention of over-vaccination can also be prevented if owners keep a record of all vaccinations that their pups receive over the years.

The vets can decide to reschedule and adjust the vaccination timing in accordance with the medical history of your dog and its current condition, but having a record of all vaccinations and other medical procedures can be handy for you and the doctors, just in case.

Ask For A Titer Test

A titer test for dogs is one of the best ways to prevent over-vaccination. With this simple test, the veterinarians can determine whether the pup has sufficient antibodies to attack certain viruses or whether it needs re-vaccination.

In some cases, if the dog has enough antibodies, your veterinarian may recommend that you postpone the annual booster or vaccination.

Speak To Your Vet About The Recommended Vaccinations

You should take the time to discuss the best vaccination for your dog with your veterinarian. It will be based on your dog’s age, health, the area you live in, and other specific and individual factors.

Remember to tell your veterinarian about any reactions you have observed after vaccination, including any behavioral changes in the pup.


Does Every Dog Need Booster Shots?

While the guidelines provided by the American Animal Hospital Association claim that vaccines can provide an immune response in dogs for up to 5 years following the vaccination, dogs do need booster shots to reinforce their immune systems as they get older.

How Long Should You Wait Between Vaccinations?

The period between the required and recommended vaccinations depends on your dog’s age. Vaccines are usually administered in three sessions in the first six months of age for puppies. Older dogs can receive their annual or booster vaccines once every year and up to once every three years, as their veterinarians recommend.

Final Words

While ensuring that our dogs are vaccinated is one of our essential obligations as dog parents, being overly protective and over-vaccinating the dog can lead to mild or severe side effects.

Make sure you speak to your veterinarian about the best vaccination schedule for your dog.

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