Thursday, May 14, 2009

Vaccine reactions

I heard that this week two of Poppy’s litter mates have become sick after their vaccines, so I thought this would be a good time to broach the subject of vaccine reactions.

The good news is that vaccine reactions are very rare, it is safe to say less than one percent of vaccinated pets experience an adverse reaction. Not vaccinating for fear of an adverse effect is not the answer. As vaccination in the general population wanes, re-emergence of these diseases is certain and the diseases we do vaccinate against are very serious or even fatal. There has been a benefit of this focus on adverse effects; increased research into vaccine safely, efficacy and duration of immunity. Vaccinations protect our pets from many potentially fatal diseases, and their benefits far outweigh the small risk of a vaccine reaction.

After their vaccination, mAfter a vaccany pets will act tired and have a decreased appetite; some will even have muscle soreness or a mild fever. As long as this resolves within 24 hours treatment is not necessary.

When vaccine reactions do occur, they can be unpredictable and manifest in many different ways. Very infrequently we see a pet have an allergic reaction to the vaccine with clinical signs such as facial swelling, hives, excessive itchiness, weakness, difficulty breathing, pale gums, vomiting, diarrhea and extreme lethargy. If a dog or cat develops any of these symptoms they should be seen by a veterinarian immediately. In most cases the patient will respond quickly to treatment with an anti-inflammatory and an anti-histamine as well as supportive care with intravenous fluids. Once this happens the pet should always be given an injection of an anti-histamine like Benedryl, before vaccination and monitored very closely afterwards.

Poppy’s littermates were not vaccinated or treated at Friendship, but from what I was told they developed extreme lethargy, decreased appetite, high fever and joint pain. The joint pain is a somewhat unusual presentation for a vaccine reaction but what I believe happened is that for some unknown reason the puppies’ immune system created an inflammatory response to the vaccine which resulted in localization of immune complexes in the joints causing pain. They were treated with a non-steroidal anti-inflammatory such as Rimadyl, as well as Doxycycline, in case the illness was related to an infectious disease. While Doxycycline is an antibiotic, it also has anti-inflammatory properties which would help make the puppies feel better.

Thankfully, all of the puppies have made a full recovery and are lucky to have such attentive owners. The puppies’ potential for vaccine reactions is something their owners will have to be aware of for the rest of the dogs’ lives. In the future, before each vaccination, pre-treated with anti-histamine should prevent a reaction.

While all vaccine reactions are an unfortunate complication, it’s crucial to bear in mind that the benefit of preventing potentially fatal diseases far outweighs the minimal risk of a reaction. The puppies must also stay on the schedule of vaccines every three to four weeks to help prevent diseases such as parvovirus. Poppy will be given her final set of vaccines next week and I will be watching her very closely for any signs of adverse reaction.


  1. Dr Hughes, you mention the odds of an adverse reaction are considered low. But how do we know? Who is counting?

    My dog became very ill and was subsequently put to sleep after her last revaccination in September 2008. I suspect my dog's illness was caused or influenced by her last revaccination with a C5 booster (the sixth one she had in her life of eight years). But as the visible signs of her illness appeared eight days after her revaccination, the veterinarian refused to consider the possibility the vaccination might have caused a delayed adverse reaction.

    I have now spent the past seven months researching this issue to investigate my suspicion that her illness (and subsequent death) could have been caused or influenced by the revaccination. During my research I discovered that my dog should not have been revaccinated at all – there was no need as the latest scientific evidence indicates that vaccines for diseases such as canine parvovirus, distemper and adenovirus are likely to provide life-long immunity. (See for example papers by Professor Ronald Schultz, an expert in immunology and a member of the World Small Animal Veterinary Association’s Dog and Cat Vaccination Guidelines Group – Refs. 1 and 2).

    So my dog underwent the risk of an adverse reaction to vaccination needlessly. I have now written a report on this topic titled: "Is over-vaccination harming our pets? Are vets making our pets sick?" This report is fully referenced and footnoted. I am currently in the process of posting this report on the internet and I will forward a link when this is completed.

    On the topic of adverse reaction to vaccination, in a paper titled "Vaccine-Associated Adverse Events", E. Kathryn Meyer notes vaccination "risks should be effectively communicated to pet owners so that informed consent can be obtained and the animal can be properly monitored and promptly treated for vaccine-associated adverse events. Unfortunately, veterinarians are hindered in this important task because of a lack of evidence-based information regarding vaccine risks."

    For example, "prelicensing safety testing of vaccines involves a relatively small number of animals, and the results are not routinely required on product labelling". These could include "rare events, events that occur after repeated exposure, and events that occur in a subgroup (e.g. specific breed, age)". Meyer also notes that "adverse event information derived from postmarketing surveillance is not routinely required on the product’s label". (Ref. 3).

    This raises the important question – why aren't these types of adverse reaction included on the product label?

    Of course, veterinarians have to play their part in post-marketing surveillance too. The WSAVA Dog and Cat Vaccination Guidelines recommend that adverse events be reported. Such adverse events include "any injury, toxicity, or hypersensitivity reaction associated with vaccination, whether or not the event can be directly attributed to the vaccine." (Ref. 4).

    In my personal experience, this type of reporting isn't happening. In my dog's case, the veterinarian wouldn't countenance the possibility of a delayed adverse reaction to vaccination. So now I, a layperson, have to do the research and make a report myself.

    Who knows how many other suspect cases might go unreported? Or how many chronic illnesses might develop after years of over-vaccination?

    Of course, if veterinarians simply stopped over-vaccinating dogs (and cats), that would go a long way to reducing adverse reactions…

    Elizabeth Hart,

    Ref. 1: Schultz, R.D. Current and future canine and feline vaccination programs. Veterinary Medicine. March 1998, 233-254.

    Ref. 2: Schultz, R.D. 2007. What everyone needs to know about canine vaccines and vaccination programs. 2007 National Parent Club Canine Health Conference:

    Ref. 3: Meyer, E. Kathryn. Vaccine-Associated Adverse Events. Veterinary Clinics of North America: Small Animal Practice, Vol. 31, No. 3, 493-513, May 2001.

    Ref. 4: Guidelines for the Vaccination of Dogs and Cats, compiled by the Vaccination Guidelines Group (VGG) of the World Small Animal Veterinary Association (WSAVA):

  2. Dr Hughes - further to my previous comment, I have emailed a copy of my report "Is over-vaccination harming our pets? Are vets making our pets sick?" direct to you at the Friendship Hospital for Animals.

  3. Please see the post on Tuesday, May 19th for my response to the above comment. I would also like to express my sympathies for Ms. Hart's loss of her dog Sasha.

  4. Vaccines is most important for every kind of pet.It is the easiest way of pets better care.

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