Skip to main content

Q&A: What Are the Side Effects of the Lepto Vaccine in Dogs?

Dr. Mark is a veterinarian. He has been working with dogs for more than 40 years.

Breathing problems are a known side effect of the lepto vaccine. What are the others, and what can you do if your dog is affected?

Breathing problems are a known side effect of the lepto vaccine. What are the others, and what can you do if your dog is affected?

Why Is My Dog Breathing Heavily and Struggling to Bark After the Lepto Vaccine?

"My dog had her yearly check and was fine, but the vet gave my dog the lepto vaccine and 6 days later she could not bark and was lethargic. They put her on antibiotics and prednisone but two months later she is still breathing heavily and her bark is hoarse.

The groomer told us that the vaccine caused heart failure. When I took her in 10 days ago for a booster, she got another lepto shot even though I asked them not to give it; 6 days later she had a "honking" episode and another today.

Why is there no information on this? What can I give them to help? THANK YOU." —L.J.

The Leptovirus Vaccine Is Not a Core Vaccine

The vaccination for leptospirosis in dogs is not a core vaccine and does not need to be given to your dog. It is possible, though, that your local vets always give the lepto vaccine if it is a problem in your area. Also, not all vets have the distemper and parvovirus on hand as a separate product, so some clinics just give the vaccines together.

Side Effects of the Leptospirosis Vaccine in Dogs

There are a lot of warnings about the side effects of the vaccine, and all vets are aware of this issue. The side effects (1) after giving this vaccine to your dog are:

  • lethargy (tired and weak)
  • swollen face
  • swelling around the eyes
  • hives (bumps all over the body)
  • breathing problems
  • vomiting
  • diarrhea
  • swelling at the injection site
  • collapse

Not all dogs experience all of the side effects. The honking episode you describe may have been a side effect of a breathing problem or it may have been a sign of nausea and your dog felt like vomiting.

Dogs can be treated for anaphylactic vaccination reactions as soon as they occur but there is no specific treatment for a later reaction. If the dog is still making the "honking" noises, you can take her in to have her throat treated with an anti-inflammatory like prednisone (2), and if the throat is irritated and looks infected she may also be put on antibiotics again.

Even without knowing the specifics in your area, I can tell you that all dogs need certain vaccines. If you would like more info on what you need before visiting the vet in the future, look at whether dogs need vaccines and which are most important.


  1. Eric Klaasen, H. L., & Adler, B. (2015). Recent advances in canine leptospirosis: focus on vaccine development. Veterinary medicine (Auckland, N.Z.), 6, 245–260.
  2. Day, MJ, Guidelines for the vaccination of dogs and cats, World Small Animal Veterinary Association, 2015.

This article is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from your veterinarian. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

© 2022 Mark dos Anjos DVM