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Ask a Vet: What’s the Strangest Vaccine Reaction You’ve Ever Seen?

A puppy came to the emergency vet with frightening symptoms. Were they caused by a vaccine or was something more serious going on?

Written by: Dr. Eric Barchas (Veterinarian)

Last Updated on January 12, 2024 by Dogster Team

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Ask a Vet: What’s the Strangest Vaccine Reaction You’ve Ever Seen?

Hyperesthesia is something I would not wish upon anyone or any creature. The condition manifests as increased pain in response to stimuli (such as gentle petting) that should not be painful. It’s commonly caused by trauma or neurological disorders, especially disorders of the spinal cord and brain. Rarely, certain uncommon types of toxicities may cause the condition. Idiopathic hyperesthesia is a disorder in which animals suffer increased pain levels for no reason that can be determined.

Recently I treated a three-month-old Miniature Dachshund puppy who was in very bad shape. Immediately upon entering the exam room I noted that she was very lethargic. She was sternally recumbent (that’s a fancy way of saying that she was lying on her abdomen and could not rise) and she was breathing really, really fast — a condition called severe tachypnea. Her respiratory rate was around 200 breaths per minute. She had a mild fever.

I examined her and found a very small lesion — a laceration or a burn — on the gums behind one of her premolar teeth. Although her respiratory rate was high I could not hear evidence of fluid in her lungs. And she was extremely hyperesthetic. Any contact with her hindquarters or abdomen or rear legs elicited pitiful vocalization, making it impossible to fully evaluate her rear end.

The owners told me the puppy had gotten a distemper/hepatitis/parvovirus (DA2PP) vaccine at a nearby pet store’s shot clinic earlier in the day. Other than that, nothing out of the ordinary had occurred. The puppy had, in the past, attempted to chew on electric cords but all of the known cords in the house had been removed or unplugged. The symptoms came on suddenly about three hours after the vaccine was administered.

A list of possibilities was beginning to form in my mind, and I didn’t like some of them.

Of course, a reaction to the vaccine was on that list. I truly hoped it was the cause, because vaccine reactions generally respond rapidly to treatment. However, in more than 14 years of practice I had never seen a vaccine reaction cause symptoms such as the ones the puppy was suffering. I was worried that something more serious was happening.

Although the owners believed they had eliminated access to all electric cords, I have learned through experience that it is not possible to completely puppy-proof a home. When puppies bite into electric cords they can receive a nasty shock and receive small, almost imperceptible burns in the mouth.

This shock jolts the nervous system, and a condition called non-cardiogenic pulmonary edema may occur, manifested by fluid building up in the lungs. It is devilishly hard to treat.

The first symptom is often an increased respiratory rate. I surmised that hyperesthesia may have developed secondary to neurological injury, or due to back strain when the puppy was shocked. Electric cord bites carry guarded prognoses — even with treatment, a significant proportion of puppies die.

Trauma and toxicity, as well as metabolic and glandular problems, also were on the list that was forming in my mind. I advised the owners of all this. Treatment was strongly recommended, but even with treatment there could be no guarantees.

The puppy was triaged and given the highest priority of any patient in the hospital. She received injections of diphenhydramine (which treats vaccine reactions) and hydromorphone (a very powerful narcotic pain killer). A CFAST showed no irregularities. (CFAST is an acronym that is short for “complete focused assessment with sonography for trauma, triage, or tracking.” It is all the rage these days among emergency vets. Basically, it’s brief evaluation of the chest and abdomen with ultrasound.) She was placed in an enriched-oxygen environment while the medications took effect. And once they took effect, I am happy to report that she was essentially cured.

The hyperesthesia was eliminated, and a comprehensive examination of the hindquarters revealed no irregularities. X-rays showed no evidence of fluid in the lungs and no evidence of trauma. Blood work and urinalysis showed no abnormalities. The puppy was hospitalized overnight for IV fluids and observation; her symptoms did not return. The tentative diagnosis, achieved by ruling out other causes, was a highly atypical vaccine reaction.

veterinarian microchipping beagle dog
Image Credit: LightField Studios, Shutterstock

About an hour later, and around the time that the Miniature Dachshund’s diagnostic test results came back, a 16-month-old terrier mix arrived at the hospital. He had developed sudden onset of lethargy at home. He was unable to stand up, and his hindquarters seemed exceptionally sensitive. There was no known history of trauma. In fact, the only unusual event was a visit to a vaccine clinic earlier in the day.

The terrier, it turned out, had received the same type of vaccine at the same pet food store’s vaccine clinic on the same day as the Mini Dachshund. And he, too, responded immediately to treatment. I braced for a further onslaught of similar cases, but fortunately I saw only two.

Both dogs went home in the morning none the worse for wear. My understanding is that the pet food store is investigating the matter. I’m guessing that a bad batch of vaccines was involved.

This story has a moral. Vaccine clinics seem like a simple way to save money on shots, but in my opinion it’s better to vaccinate pets at established family veterinary offices. You establish a relationship with the vet, and good family vets also will take the time to sit down and discuss which vaccines your dog actually needs, whereas some vaccine clinics simply work to pump as many shots as possible into dogs.

But here is where the real benefit comes in: Family vets usually stand behind their work. If something goes wrong, they will be there to help you. In situations such as this, family vets could be expected raise hell with the manufacturer of the vaccines, or waive the expenses of the treatment. Your vet bills might even be paid by the vaccine manufacturer.

If you go to a vaccine clinic, by the time there is a problem the clinic usually has closed and the staff has cleared out. You’ll be stuck going to the emergency clinic instead. The emergency vet can’t raise hell with the vaccine manufacturer, because he won’t know which one to call. The best he can do is to call the pet food store in the morning and start an investigation.

Finally, don’t let this story scare you off of vaccination, especially for puppies. Yes, I saw two dogs suffer from crazy vaccine reactions in one evening. But both dogs recovered fully.

In contrast, I have seen hundreds of dogs suffer and sometimes die from parvovirus. The benefits of judicious vaccination almost always outweigh the risks.

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Got a question for Dr. Barchas? Ask our vet in the comments below and you might be featured in an upcoming column. (Note that if you have an emergency situation, please see your own vet immediately!)

Feature Image Credit: Pressmaster, Shutterstock


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