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Dog Vaccinations

A woman with dark brown hair wearing blue shirt and blue gloves is holding up a Yorkshire terrier

What are dog vaccines and why are they important?

Vaccines are biological products that are created in order to prepare a dog’s immune system to withstand infections. Certain bacteria and viruses are put into the vaccines, but they are modified in a way that does not cause active infection when it enters your dog’s body. Instead, the vaccine trains your dog’s immune system to recognize and destroy the real disease if your dog is ever exposed to it.

Vaccines are very effective, and while some may not prevent 100% of a disease, they can significantly reduce the severity of the disease’s clinical signs, even preventing death in some cases. Vaccines can prevent highly contagious diseases that are transmissible to other animals and people. Dogs that are very young or immunocompromised may not be able to receive vaccines, but if the adult dogs in their neighborhood are all vaccinated, then this will dramatically reduce the risk of illness for un-vaccinated dogs. This is called herd immunity.

What are the core vaccinations for a dog?

Core vaccinations are vaccines that are considered essential for all dogs by the American Animal Hospital Association, which is an organization that sets the standards for quality and excellence in veterinary medical care. There are four core vaccinations for dogs, three of which are usually combined into one vaccine injection. These core vaccines are:

1. Canine parvovirus

Parvovirus is a highly contagious virus that is shed through feces and can exist in an environment for several years. The virus attacks the lining of the small intestine, causing significant diarrhea and fluid losses. Other clinical signs include loss of appetite, fever, and vomiting. Puppies under four months of age are at the greatest risk because their immune systems are not yet fully developed to help fight off the infection, and their clinical signs are so severe that many puppies can die from parvovirus. There is no cure, and aggressive supportive care is necessary in order to help puppies overcome their illness.

2. Canine distemper

Distemper is a highly contagious virus and can affect multiple body systems like the digestive tract, the respiratory system, and the nervous system. Puppies have the highest risk due to their weakened immune systems. Severe clinical signs can result in death, and if puppies survive an infection, then some may have chronic issues like poor gastrointestinal health or neurological deficits. There is no cure for distemper.  

3. Hepatitis

Canine infectious hepatitis is caused by a virus. It can be shed through urine, feces, saliva, and even nasal discharge. It is highly contagious but can only be spread to other dogs and not humans. Hepatitis can affect multiple organs and sometimes appear like kennel cough in young puppies. Severe infections can cause liver failure and death, and there is no cure for this virus. Treatment is usually focused on supportive care and antibiotics for any secondary bacterial infections.

4. Rabies

Rabies is the deadliest of these viruses because it is 100% fatal without treatment. Skunks, foxes, bats, raccoons, and coyotes can be carriers, and rabies can be spread to pets and people through bite wounds. It is traditionally thought to make animals appear “rabid” or aggressive, but depending on the stage of the disease, some animals may seem docile or tame due to the dulling effect on their nervous system. If you or your dog are bitten, then you must seek medical attention immediately. Because of the highly contagious and deadly nature of this virus, rabies vaccination is required by law in most states.  

Non-core vaccinations for dogs

Other vaccinations available for dogs are considered non-core vaccines. This is because these vaccines might not be considered essential for all dogs unless they are at a higher risk of contracting the disease. The risk depends on several factors, including geographic location, travel history, and exposure to other dogs.

1. Bordetella

Bordetella bronchiseptica is a bacterium that is commonly implicated in cases of “kennel cough,” a term that refers to a highly contagious upper respiratory illness in dogs. Puppies and dogs that are kept in close contact with other dogs (e.g. at a kennel) have an increased risk of developing an illness. Besides coughing, other clinical signs include vomiting, lack of appetite, sneezing, and trouble breathing. In severe cases, the infection can spread to the lungs and cause life-threatening pneumonia.

2. Canine influenza

LikeBordetella, canine influenza is highly contagious and is more commonly seen in cases where dogs are kept within confined areas. Two of the most recent outbreaks in the United States occurred in doggie daycares and boarding facilities. Influenza can cause severe upper respiratory clinical signs, especially prolonged coughing, and it can also progress to pneumonia in some cases.

3. Leptospirosis

Leptospirosis is a bacterial disease that is primarily shed through the urine of other animals, especially wildlife. It can spread to other pets and to people through contact with urine, and the bacteria can also be found in water sources. Clinical signs like fever, vomiting, diarrhea, and abdominal pain are common, but leptospirosis can also progress to kidney and liver failure very quickly.

4. Lyme disease

Lyme disease is a bacterial disease that is shed through the bite of an infected tick. Some dogs can be carriers of the disease and might never show clinical signs while others can appear weak and lethargic. Other clinical signs include fever, limping, and loss of appetite. Infection can be lifelong, and dogs living in the Midwestern and Northeastern United States are at a higher risk for the disease.

Vaccination schedule

a blonde woman is giving a small white puppy medicine as two small children watch

Most puppies should start to receive their first sets of vaccines around eight weeks of age because this is around the time that the immunity received from their mothers will start to diminish. Puppies usually receive theirBordetella vaccine and a combination vaccine that includes distemper, parvovirus, parainfluenza (another virus that can cause “kennel cough”), and the adenovirus that is responsible for canine infectious hepatitis.

Three weeks later, or around eleven to twelve weeks of age, puppies can receive their influenza and leptospirosis vaccines. Their distemper combo vaccination, sometimes notated as DHPP or DAPP, should be repeated or boostered around this age. By the time a puppy is fifteen to sixteen weeks old, he will receive his rabies vaccine as well as appropriate boosters for the DAPP and leptospirosis and influenza vaccines. It is important to make sure that your puppy has at least fourteen days in between his vaccine boosters. This is because the efficacy of the first vaccine can decrease if a second vaccine is given early.

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Vaccine effectiveness

Once a puppy’s vaccine series is complete, most vaccines will be effective for one year. When your dog is an adult and depending on the vaccine manufacturer, your dog’s next DAPP and rabies vaccines may provide immunity for up to three years. A vaccine like a leptospirosis, influenza, and Lyme disease will be effective for one year after appropriate boostering. In high-risk areas like boarding facilities and doggie daycares, theBordetella vaccine may be recommended every six months instead of one year.

Possible side effects

Vaccinations can have side effects. The majority of pets show no signs, and some may be slightly painful at the injection site. In the case of intranasal vaccines likeBordetella, your dog may have some minor sneezing for a day or two. If your dog is having a vaccine reaction, then he may experience fever, lethargy, vomiting, diarrhea, loss of appetite, hives, and facial swelling. In rare but severe cases, anaphylaxis is possible. Make sure to contact your veterinarian right away if your dog is having signs of a reaction.


Even though side effects are possible, the benefits of vaccination far outweigh the risks. Vaccines are effective and inexpensive, whereas the treatment and supportive care necessary for these illnesses can be expensive and, sadly, unsuccessful. Vaccinations are important because they can protect you, your best furry friend, and those who cannot receive vaccines. 

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Meet The Author

Author Dr. Erica Irish

Dr. Erica Irish

Erica has worked in the veterinary field since 2006, starting out as a veterinary technician before graduating from the UF College of Veterinary Medicine in 2013. As a general practitioner in an animal hospital, she has many interests and is especially interested in dermatology, cardiology, internal and integrative medicine.

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