What Happens if a Dog Gets Vaccinated Twice?

Being a dog owner means getting all measures and vaccinations to prevent diseases. While it’s essential to immunize our pets, we should be cautious about what happens if a dog gets vaccinated twice. The kind of vaccination, frequency, and a pet’s medical history can help us discern about getting our dogs vaccinated again. 

What Happens if a Dog Gets Vaccinated Twice?

While there may be no adverse effects right away, it isn’t ideal to vaccinate a dog twice. If we allow unnecessary vaccinations, our dogs may suffer from allergic reactions, autoimmune diseases, behavioral changes, and rarely, death. 

To make sure we prevent such unfortunate things from happening to our furry friends, we need to understand the effects of over-vaccination.

Allergic Reactions

Studies show that young adult small-breed dogs with multiple vaccines per vet visit were at greatest risk of vaccine reaction within three days of vaccination. However, this isn’t the case for multivalent vaccines, which include vaccines for parvovirus, parainfluenza, or bordetella for kennel cough.

While allergic reactions may disappear in a day or two, some cases result in more severe problems. We must bring our dogs back to the veterinarian if there are one or more types of these allergic reactions for a prolonged period:

  • Reactions at the Injection Site: Redness, swelling, pain, or irritation at the area of injection. Abscess or collection of pus may also form at the site. 
  • Anaphylaxis: Symptoms include sudden vomiting, diarrhea, drowsiness, weak yet fast pulse, facial swelling, and seizures. Although rare, anaphylaxis can be life-threatening and result in cardiac or respiratory failure, shock, and even death. 
  • Respiratory Problems: Intranasal vaccinations may cause sneezing, mild cough, or discharge from the nose. 
  • Decreased Appetite: Happens one or two days after vaccinations. May come alongside mild fever and depression.  
Dog being prepared by volunteers before being vaccinated

Immune System Overload 

A dog’s immune system consists of two major classes that are complementary and interdependent. The first one is cellular immunity that acts as the dog’s primary immune defense system. The other one is the humoral immunity, which produces antigen-specific antibodies for secondary defense. 

Once a subset of these classes becomes dominant, vaccines bypass the cellular immune system and stimulate the humoral system instead. As a result, the humoral system instills dominance over the major line of defense. Subsequently, this reverses a dog’s natural immunological scheme and turns the immune systems inside out. 

Behavioral Changes

Every vaccine contains two elements: the actual virus that creates an immune response to, like parvovirus, and an immune adjuvant that boosts immune response. 

Vaccine adjuvants usually include a variety of highly toxic compounds such as mercury, aluminum, and MSG. When vaccine adjuvants create prolonged activation, the brain may suffer from inflammation, resulting in a dog’s behavioral changes. 

Some dogs become overly aggressive to both humans and animals due to double vaccination. Over-immunization may result in things like:

  • Hypersensitivity of all senses
  • Coughing, gagging, or choking when swallowing liquids 
  • Ferocity, violence, agitation, and rage 
  • Sudden or unprovoked attacks 
  • Suspicions and irrational fears 
  • Either a great desire or extreme fear of water 
  • Excessive focal licking and sexual drives
  • Unwarranted or constant erections
  • Compulsive or obsessive chasing and biting  
  • Sensitivity to noise, tight clothing, and close places
  • Involuntary urination
  • Aimless wandering and vocalization

Tips on Avoiding Over-Vaccination

Vaccines are good, particularly if administered the proper way. One way we can ensure this is to arm ourselves with the critical information about dog vaccinations, so we would know what should and should not happen per vet visit. These are a few things we need to remember when heading to a pet clinic for immunization. 

Educate Yourself About Vaccination Basics

Our dogs should receive core vaccines between eight to 16 weeks of age to protect them from serious, life-threatening diseases. This includes canine distemper, canine parvovirus, and canine adenovirus. The rabies vaccine is also a core vaccine, although a dog can only have it once at age 12 to 16 weeks. 

Meanwhile, non-core vaccinations apply to dogs whose local environment, lifestyle, and geographical location put them at risk of contracting certain infections. These vaccines are parainfluenza, bordetella, Borrelia burgdorferi, and leptospirosis. 

Keep a Record of Your Dog’s Vaccination History

We can bring your dog’s vaccination checkup records. In this way, we can have a better understanding of your dog’s health. Likewise, we can see changes in a pet’s health.  

A veterinarian holding a puppy

We may set or adjust vaccination schedules depending on the dog’s medical history, test results, injuries, surgeries, and prescribed medication. Thus, it’s crucial to keep the doctor’s card handy to ensure we get all the information and we can proceed according to the pet’s needs.

Request for a Titer Test

Another way we can avoid double vaccination is to request a titer test, which is an antibody blood test that determines if a previous vaccine is still protecting a dog’s immune system. If the vaccine continues to produce antibodies, then there’s no need to revaccinate yet. 

Be Open to Discussions 

You can ask for prescribed vaccinations depending on your location. Don’t be afraid to talk with us about the most important vaccines your pet must take immediately, as well as those you can avail as the dog grows. 

Discuss the dog’s health issues or behavioral changes after vaccination. Consider vital details like age, health status, and lifestyle before deciding. Such information can help us provide proper vaccination or treatment for your pets. 

Related Questions

Does My Dog Need Booster Shots?

Guidelines from the American Animal Hospital Association show that commercially available vaccines can provide a protective immune response for up to five years. However, dogs require regular booster injections as they grow old to reinforce their immunity from initial vaccinations.

How Long Can You Leave Between Dog Vaccinations?

The waiting period between each vaccine should depend on the pet’s age. If it’s a puppy, vaccination usually happens three times in a period of six months. After that, it could be yearly or once every three years.


Our dogs need all the care and love from all of us. However, it wouldn’t be helpful to be overzealous in vaccinating them twice. Be sure to consult with us on the best way to move forward with your dog’s immunization to avoid negative effects.

Categories Dog

Doctor Joe Alcorn received his Doctor of Veterinary Medicine from Colorado State University in 1981, and founded Care Animal Hospital in 1991 in Temecula, California. He is a member of the American Veterinary Medical Association.