Evidence Update: Vaccination and Autoimmune Disease

One of the potential adverse effects of vaccination is the triggering of autoimmune diseases in susceptible individuals. There is some evidence in humans, for example, that the routine MMR vaccine (which prevents measles, mumps, and rubella) can trigger an autoimmine disease, called ITP, which destroys platelets and reduces a patient’s ability to form normal blood clots. The evidence suggests this occurs in roughly 1-3 children for every 100,000 MMR vaccinations.

While this is a real and serious risk, it is important to note that not only are the diseases prevented by this vaccine a much greater risk, but it turns out that these disease can also cause ITP and at a much higher rate than the vaccine (1 child out of every 3,000-6,000 cases). Therefore, the benefit of vaccination is clearly greater than the risk in this case.

There is, as always, far less data to determine what, if any, risk of autoimmune disease there is in vaccination of dogs and cats. Both ITP and IMHA, another autoimmune disease involving destruction of red blood cells, occur in dogs, and these have been reported to follow vaccination. However, the relevant research literature is sparse, flawed, and inconsistent. The bottom line from my previous review of the literature was this:

Bottom Line

  • Little evidence vaccination causes IMHA/ITP
  • No consistent temporal association
  • Data are weak
  • Overwhelming majority of vaccinated animals do not develop these diseases
  • Infection can be a greater risk for IMHA/ITP than vaccination
  • Don’t vaccinate more than necessary
  • Don’t vaccinate less than necessary
  • Don’t avoid vaccination out of fear of IMHA/ITP

A small piece of additional evidence was recently presented at the American College of Veterinary Internal Medicine (ACVIM) 2017 Forum.

Moon, AKB. Veir, J. Vaccination Behavior and Adverse Events in Dogs Treated for Primary Immune-Mediated Hemolytic Anemia (Abstract HM17) ACVIM Forum, National Harbor, MD, 2017.

This study surveyed the owners and veterinarians of dogs who had been diagnosed with IMHA. Such dogs are frequently not vaccinated once they recover from the disease because of concerns that vaccination might trigger a relapse. This is often done even when there is no specific reason to think vaccination triggered the initial episode. It is a reasonable precaution, but since it is not clear that vaccination actually is a risk factor for ITP or IMHA, it is possible that these dogs are being left vulnerable to infectious diseases unnecessarily.

In this small study, survey results were available for 44 dogs. There were several relevant findings:

  1. The average time from most recent vaccination to the initial onset of IMHA was 351 days. Such a long period makes it unlikely that vaccination was a major trigger for IMHA in many of these dogs. It still might have been in the subset who were vaccinated closer in time to the onset of their illness. This study found no such temporal relationship, but a different study design would be necesary to confirm that.Previous studies have found only a small proportion of IMHA cases received vaccinations in the 2-4 weeks before the onset of their illness, and most found no difference in recent vaccination rates between dogs who developed these diseases and comparison dogs who did not. So far, the overall data suggests that vaccination is rarely a proximal trigger for these autoimmune disease, though whether they play a role as an overall risk factor isn’t known.
  2. About half of the dogs had not been vaccinated since their IMHA diagnosis. This is consistent with the common practice of many vets to eschew vaccination in dogs who have had a history of autoimmune disease. However, about half of these dogs did receive vaccines after their diagnosis, and almost all of these were rabies vaccines. This is likely because rabies vaccination is legally required in most of the U.S. and exceptions are not always allowed for dogs with a history of autoimmune disease.Only 2 of the 21 dogs who were vaccinated following their IMHA had any reported adverse reaction. These two reactions were typical of the acute hypersensitivity reaction seen with vaccination. No relapse of IMHA or other autoimmune disease was reported in the vaccinated dogs. This suggests that such dogs may not be more sensitive to vaccination than other dogs, though again the size and methodology of this study is not adequate to demonstrate that with any certainty.
  3. Though this is just a small bit of data, it does fit into the larger context of existing evidence in dogs, and the much more comprehensive evidence in humans, suggesting that vaccines play an extremely small role, if any, in triggering such autoimmune diseases, While caution is warranted, and certainly unnecessary vaccination should be avoided on principle, there is no justification for extreme and confident claims that vaccines are a major cause of these autoimmune diseases in our pets or that what risk may exist outweighs the benefits of appropriate vaccination.
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5 Responses to Evidence Update: Vaccination and Autoimmune Disease

  1. DogsMum says:

    You may sound knowledgeable and I admire the fact that you do refer to scientific evidence for every article. However. I lost my dog to IMHA as a result of vaccination, L4 containing thiomersal to be precise. Until that moment my boy was healthy and never required any medical attention or help.

    Since then I have also met at least 30 dog owners who lost their dogs to IMHA as a result of L4 vaccine. I have then switched the vet and now work with the one who spent several years studying IMHA with particular interest in the link between vaccinations and the condition (as well as other side-effects)

    They DO NOT use L4 vaccine in their practice because since it was introduced by other surgeries, the number of dogs dying from IMHA increased from 1-2 per year to at least a dozen! True, there is no firm evidence between the disease and specific ingredient, but one has to be blind and brain-washed NOT to see the link.

    I do still advocate vaccinations because I am not from the dark ages and do understand the importance of immunisation, but I would strongly disagree with the fact that vaccine is not linked to IMHA as well as several other fatal conditions.

  2. skeptvet says:

    I understand why your experience leads you to this conclusion. The problem is that when others have entirely different experiences if there is no controlled data you end up with clashing anecdotes and everyone simply chooses to believe their own and ignore everyone else’s. That vaccine has been widely used, and we certainly use it often at my hospital. We’ve seen no change in the occurrence of IMHA and have not had any dogs develop IMHA associated with receiving this vaccine. Likewise, since the vaccine was introduced, there is no evidence of any increase in the incidence of IMHA. And if you think the thiomersal is responsible, why has this association not been seen in humans, when that preservative was widely used for many years, or with all the other vaccines containing the same ingredient? Again, all you have is anecdotes and opinions, and while the conclusion you’ve drawn is reasonable based on these anecdotes, it is not consistent with the experiences of many others. Either we then give up on determining the truth and just all believe our own stories, or we rely on controlled research data rather than anecdotes.

  3. As another evidence-inspired practitioner, I am grateful for the time and effort Skeptvet puts forth in this continuing discussion. An anecdote, if you’ll allow. A mid-career small fluffy dog with known history of immune-mediated thrombocytopenia (low blood platelets, leading to bruising/bleeding) arrived for a rabies booster. Young couple owners, very nervous about boostering a dog with an immune mediated disease. We’re in PA and have a rabies vaccine law. The law, though, allows us to make a medical decision not to vaccinate, if the attending vet thinks it might be risky. I thought it was risky, to the relief of the owners, completed the exam, signed a rabies waiver (which is sent to our Dept. of Ag.), and off they went. 10 days later, bruising, petechia–platelets too low to count on CBC. This from not vaccinating a little fluffy dog. I cheekily offer this anecdote as proof that not vaccinating for rabies can lead to ITP. I did tell the owners how glad I was to not vaccinate, as this case would have left us all indelibly persuaded that the episode was vaccine-related, when it was very clearly not. I remain not inclined to booster this dog, he remains “lapsed” on his rabies in the eyes of the law.

  4. Val says:

    I recently adopted a 10-year-old dog who had never been vaccinated. Before I could get her her shots, she was diagnosed with SLO and my vet didn’t want to vaccinate her. I don’t know if I should second-guess this decision or not.

  5. skeptvet says:

    If the dogs has truly never been vaccinated, then there is some significant risk from several infectious diseases, and vaccination makes sense. That said, it is very rare to see a dog that age who has never had vaccines, and often they have them as puppies and the records aren’t there. You could get titers checked which would at least indicate past vaccination if positive.

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