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June 21, 2012

As promised over these many months, I did some digging to find out exactly how RARE what happened to Lilly after her rabies vaccination earlier this year really is. Today, the answer.

To recap: Lilly developed meningoencephalomyelitis / meningoencephalitis (inflammation of the brain and lining of the brain and spinal cord) after an adverse vaccine reaction to a rabies vaccine given January 23, 2012.

Answers to most of the frequently asked questions can be found in this 5-part Adverse Vaccine Reaction FAQ.

When I posted those FAQ, I didn’t yet know how to answer the incidence rate question people so often ask.

And, even now, after reading several studies published in veterinary science journals and after wading through the data sent me in response to my USDA Freedom of Information Act Request, I cannot give you a real incidence rate because such things are hard — even for researchers — to calculate because you’d have to know exactly how many of the vaccines were given and then figure from there. That big number is almost impossible to come by.

However, here is what I can tell you:

USDA Reports 2007-2011

Of the 22 adverse vaccine event reports over 5 years that the USDA sent me (2007 – 2011) for rabies vaccines made by the same company as Lilly’s vaccine and given to dogs:

  • NONE resulted in meningoencephalomyelitis / meningoencephalitis.

The data I received did slop over into March 2012. However, our own adverse vaccine reaction report was NOT included.

I have an email into my case coordinator, asking him to check and confirm that our report is indeed on file with the USDA and asking why it wasn’t included in the data I received back. (I have NOT heard back from him.)

Granted, as friends (including veterinarians I know) have pointed out, the government moves at glacial speed, so there is a chance our report from early February 2012 isn’t fully recorded yet.

HOWEVER, it does make me doubt the information I received.

It’s also important to note that reports to the USDA (or to vaccine makers, for that matter) are entirely voluntary. That also can skew the results since adverse vaccine reactions are likely under reported. For example, we never reported any of Lilly’s earlier “mild” reactions.

Because such Freedom of Information Act requests have to uber specific. I ONLY asked for reports for essentially the same vaccine Lilly received — not all rabies vaccines by all makers because I’d literally have had to make separate requests for every single rabies vaccine maker.

Study Published in 2008

In the three-year period studied (2004-2007), where it’s estimated that 120 million doses of rabies vaccine were distributed in the United States, there were 246 adverse event reports in dogs to the USDA, where rabies was identified as one of the vaccines given.

  • None were noted as being meningoencephalomyelitis / meningoencephalitis or neurological.

In that same three-year period, there were nearly 10,000 adverse event reports (all animal species) to manufacturers of rabies vaccines. The study authors report, “The general pattern in the manufacturers’ summaries (data not shown) did not appear to differ substantially from patterns associated with vaccines for dogs reported elsewhere.”

They go on to say that “… most reports could be categorized as acute hypersensitivity or local or systemic events.”

Also, the authors recommend that all adverse vaccine events be reported “to the vaccine manufacturer and to the CVB [UDSA].”

*emphasis mine

[Postmarketing surveillance of rabies vaccines for dogs to evaluate safety and efficacy; JAVMA, Vol 232, No 7, April 1, 2008]

Study Published in 2005

These researchers took 2-years of data from a large, national veterinary chain of hospitals, which covered more than 1.5 million dogs. They looked for adverse vaccine events within 3 days of any vaccine being given.

  • 4,678 dogs had a reaction treated within 3 days, which puts the incidence rate at 38.2 per 10,000 dogs
  • 65.8% were coded as “vaccine reactions”
  • 31.7% were coded as “allergic reactions”
  • 1.7% were coded as “anaphylaxis”
  • 0.1% were coded as “cardiac arrest”
  • However, none were reported in the study as being neurological in nature.

The predominant symptoms reported included:

  • Facial swelling, especially around the eyes
  • General itching all over
  • Vomiting
  • Local swelling, itching, soreness at the injection site
  • Systemic, nonspecific signs (fever, lethargy, anorexia … 5.5%)

[Adverse events diagnosed within three days of vaccine administration in dogs; JAVMA, Vol 227, No 7, October 1, 2005]

Study Published in 2002

These researchers looked at 311 cases reported between 1994 and 2000 in Japan. They broke the adverse vaccine reactions into 5 categories:

  1. Respiratory and/or cardiovascular symptoms
  2. Dermatological symptoms
  3. Gastrointestinal symptoms
  4. Neurologic symptoms
  5. Others

The report says that 27 of the 311 dogs received a rabies vaccine. It goes on to say, “Two dogs that received the rabies vaccination showed neurological symptoms.”

Of the 284 dogs that received non-rabies monvalent or mixed vaccines, “only one dog showed neurological symptoms.”

[A retrospective study on adverse vaccine reactions to canine vaccines in Japan; J Vet Med Sci, 64(9): 851-853, 2002]


So, how rare is what happened to Lilly?

Well, the best I can say is that I only found:

  • One study that says 2.8% of adverse vaccine reactions involve ataxia.
  • Another study reports just 3 adverse vaccine reaction cases in 6 years that were “neurological.”
  • I found ZERO references to meningoencephalomyelitis / meningoencephalitis in any of the studies that cover roughly from 1994 to 2011.


I have a bunch more interesting stuff I uncovered in my reading / research, but I’m exhausted. The posts this week have worn me out.

Pro-Vaccine, Anti-Vaccine? Reflections After an Almost Deadly Adverse Rabies Vaccine Reaction

Why Not Vaccinating a Dog is a Big Deal

Adverse Vaccine Reaction: What I Didn’t Know, When I Didn’t Know It

So, later, I’ll have to share the other tidbits, including things that increase a dog’s risk of having an adverse vaccine reaction and some of the CRAZY kinds of adverse reactions dogs can have to a vaccine.

If I feel up to it, tomorrow’s post will be a bit of a rant about my own “incidence data.”



About the Author Roxanne Hawn

Trained as a traditional journalist and based in the Rocky Mountains of Colorado, USA, I'm a full-time freelance writer for magazines, websites, and private clients. My areas of specialty include everything in the lifestyles arena, including health and home, personal finance and other consumer interests, relationships and trends, people and business profiles ... and, of course, all things pet related.

I don't just love dogs. I need them in my life. Seriously.

  1. Rox, I’m wondering what you would have come up by using the more general search term “encephalitis.”

    I get it that your neurologist was ultra-specific in giving you that exact diagnosis of meningoencephalomyelitis / meningoencephalitis — he was coming up with a term that included all of her symptoms. But my understanding has always been that encephalitis is a fairly common side effect after vaccination, even with people.

    1. Thanks, Hilda, for the question. I did indeed go looking for *any* neurological diagnosis / symptoms (not just the uber specific diagnosis Lilly got) and found very little in the data sets / research I used. It’s both a combination of likely rampant under reporting of these events and just a roll of the dice on what cases were included in these various studies.

  2. You are the only person I’ve come across that has heard of this reaction. Our dog had a terrible reaction to his first puppy shots and nearly died. I took him to a different vet and they told me that some dogs are allergic to something in the vaccine and there was a different one that could be used instead. Our dog didn’t have any trouble again once he was getting the alternate vaccine.

  3. It’s frustrating that the reports don’t instill more confidence. However, it is interesting to know that Lilly is the only reported case of this type of reaction. Poor girl – I hope she continues to improve.

  4. I’m glad you have some answers, although I’m not sure I feel any better knowing the percentages. 🙁

    Once I’d found your blog and started reading up about Lilly and the hell you all have been going through, I was concerned about the rabies vaccine in my dogs. I did ask my vet about this side-effect when Delilah had her yearly and was told it is “extremely rare” which didn’t make me feel any better either. 🙂

    I am very vocal and verbal about how we over vaccinate in this country and I am very particular with what vaccines I give my dogs. In fact, I have a twice a year chat with my vet about what I should vaccinate for.

    Since rabies is a REQUIRED vaccine, I think the best thing we can do (IMO) is to educate ourselves about side-effects and be diligent in monitoring our dogs after vaccinations.

    I also think many vaccines last far longer than we are told and that is something that needs to be addressed as well.

    I will continue to send good thoughts your way. Thank you for posting about such a personal experience.

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