Evidence Update: Dodds Study on Vaccine Dose in Small Breed Dogs

I have been able to get a look at the published paper for the study I recently discussed by Dr. Jean Dodds investigating  giving lower doses of vaccine to small breed dogs. There is nothing in the published report that changes my earlier conclusion. This study adds nothing of substance to our understanding of optimal vaccination practices. In design and execution, it is simply a marketing tool to promote a set of pre-existing beliefs about vaccination, and in itself does not help to clarify what optimal vaccination practices might be.

The argument Dr. Dodds seems to be making contains a number of elements I agree with and believe to be supported by good science:

  1. The effectiveness and duration of immunity vary by vaccine type and with many other factors, but in general core canine vaccines are very effective at preventing illness and likely most pets who receive the initial vaccine series at the appropriate time are well-protected for at least 3 years and probably much longer.
  2. Vaccines can have adverse effects, and while these are rare they can be potentially serious. The precise factors that make some individuals more susceptible to such reactions than others are unclear, but size appears to be a factor, with small-breed dogs reporting more reactions that larger breeds. (this is quite a bit more restrained than previous statements she has made about “vaccinosis” in small animals)
  3. Avoiding unnecessary vaccination in animals already immune to particular infectious diseases is a desirable goal.
  4. Titers can often tell us if an animal is already immune, depending on the disease in question, though they generally cannot tell us if the animal is vulnerable to a disease since they only reflect part of the overall immune response.

She adds to these a number of claims which are not supported by good evidence, including most of the claims related to this specific study.

The dose of canine distemper virus (CDV) and canine parvovirus vaccine (CPV) vaccines can be reduced to 50%, but not more, for small breed and small mixed breed type dogs, based on body weight, and still convey full duration of immunity.

She states this in the introduction, indicating it is a pre-existing belief she intends to buttress with this study. However, her citations for this very clear and specific claim include three of her other papers expressing this opinion and an editorial from 1999 discussing concerns among practitioners about vaccination practices. No specific research is cited that supports this claim. And elsewhere in the paper, she makes it clear that the claim is actually based primarily on her personal experience, aka anecdotal evidence.

In the informed consent sheet for clients, she says “Clinical experience has shown…” and “One of the principal investigators has nearly five decades of clinical and research experience with vaccinations in companion animals. This experience has shown…” and then repeats this claim. It is not a claim supported by research evidence but simply something she has come to believe based on patients she has seen, and it should be clearly presented as such, as mere opinion appropriate for generating a hypothesis but not for making confident claims.

The only relevant research she cites is one study in which children were shown to have an adequate protective response to a lower quantity of Hepatitis B vaccine. This was tested primarily to reduce the cost of vaccination and make vaccination available to more people, not to avoid adverse effects. But in any case, it doesn’t validate the general concept that vaccines should be dosed by body weight, which is not accepted vaccine science in human or veterinary medicine.

As for the study itself, it suffers from many serious flaws that likely would have prevented publication in an ordinary veterinary journal, which may be part of why it appears in the journal of the AHVMA.

The first issue is selection bias. The subjects were recruited by an announcement on Dr. Dodds’ web page and emails to “holistic veterinarians.” This does not appear to have been very successful since only 13 animals were recruited. But in any case, these likely represent an unusual patient population, since “holistic” veterinarians, and of course Dr. Dodds, recommend quite different approaches to preventative and therapeutic healthcare than most vets, including different vaccination practices. These animals may not be sufficiently similar to pets that receive standard veterinary care, including with respect to their vaccine history. This would limit the ability to generalize any results to other populations.

Another problem was the lack of any standard definition for “a half dose of vaccine,” which is what participating vets were told to give. While all used the same specific vaccine, this vague description of the main intervention being tested allows for a lot of unpredictable variation from subject to subject, and makes it hard to compare with any other research that may be done. The specific antigenic load given would be much more useful information at this stage of research.

A core problem with the study is that it did not address any of the underlying issues of whether giving a half dose of vaccine would protect dogs as well from disease or reduce the number of adverse vaccine reactions. Neither of these subjects was evaluated in any of the study dogs. All that was done was that antibody levels were measured before vaccination and at 4 and 6 months later. Here are the main results:

DODDS - J Am Hol Vet Med Assoc  table 1

All dogs had titers considered indication of immunity before being vaccinated. Most, but not all, dogs had an increase in their titer after vaccination at 4 months (9/13 for CPV and 11/13 for CDV) and 6 months (6/8 for CPV and 3/8 for CDV). This tells us, at most, that a smaller amount of a vaccine than usually given promotes some increase in antibody levels for CPV and CDV for some dogs. This, unfortunately, tells nothing about how to best vaccinate dogs to protect them from these diseases while minimizing any adverse health effects.

(The difference in the number of samples at 4 and 6 months reflected that while all dogs had blood samples taken at both times, “5 dogs had samples drawn at 6 months but these were inadvertently discarded.” Accidentally throwing out nearly ¼ of your samples is a pretty serious error in any study, and raises questions about the validity of the data as well as the conclusions.)

These data, even if accepted as legitimate, do not answer any of the pertinent questions, such as whether dogs receiving half of the usual vaccine dose would be protected as well long-term or healthier and less likely to experience health problems than dogs receiving the usual vaccine dose. The study doesn’t, in other words, provide any real evidence to support or refute the claims Dr. Dodds and many other “holistic” vets make about the best vaccination practices. And given she has admitted that she had no intention of following these dogs further or conducting any larger trials based on this “pilot” study, it is pretty clear that the only purpose of this study was to generate ammunition for a marketing campaign to promote ideas about vaccination that Dr. Dodds has developed entirely based on personal experience and belief.

I have addressed both the evidence concerning risks and benefits of vaccination and the issue of using titers to help make vaccination decisions. Limitations in the available evidence make a variety of different practices equally justifiable. While I probably vaccinate less than many conventional vets, I refrain from making definitive statements beyond the evidence about the effects of various approaches to vaccination. Dr. Dodds’ position is somewhat intermediate between the rabidly anti-vaccine views of some holistic vets and the unthinking annual vaccination too often still recommended by many conventional vets, and she and I are probably not too far apart in principle. However, she chooses to emphasize the risks of vaccination (especially in places where, unlike this article, she talks about nonsense like “vaccinosis”), and she makes confident claims about the best vaccination approach that she presents as science-based but which really are simply her opinion.

In this study, she has provided the illusion of scientific evidence to support these claims, but the reality is that this study is too flawed in design and execution to add anything useful to the question. Unfortunately, Dr. Dodds and others are already promoting it widely as evidence that their preferred vaccination approaches are better for patients than those of others, including the current most evidence-based guidelines. This is a misleading misuse of science consistent, unfortunately, with her approach in many other areas.

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18 Responses to Evidence Update: Dodds Study on Vaccine Dose in Small Breed Dogs

  1. L says:

    I tell people to find a traditional veterinarian that you trust and that your pet likes. And then listen to him. Too much misinformation on the internet.
    How can a vet that has not examined your pet or know it’s history advise you?
    Common sense, really.

  2. v.t. says:

    Glad you had a chance to see it, skeptvet, thanks for your take on it.

    I don’t know what vets are saying about the study, but pet owners are drooling all over it. To me, that’s a big problem (propagation of a small, poorly designed pilot study that produces little to no evidence for the claims). As is common in woo-society, more and more pets are at risk if their owners blindly take opinions such as Dodds’ as undeniable evidence.

  3. kitty says:

    “I tell people to find a traditional veterinarian that you trust and that your pet likes. ”

    I agree, the issue is finding the one you can trust. What do you do if a vet is deliberately lies to you? I trusted my vet, maybe not as much as the previous one who unfortunately moved hundreds of miles away, but I was OK with this one. Then to my question of if/when they are going to have a new 3-year Purevax vaccine, she told me how this vaccine makes cats incredibly sick and how a Merial rep told her at a conference that they really only recommend it for barn cats.

    Now I know this isn’t the case – skeptvet for example mentioned that their clinic uses 3-year Purevax, other vets are using it. Even the clinic director mentioned a few months ago in an email that the reports have been positive. I didn’t say anything – too shocked to reply, and really, how? I’ve been going to the clinic for almost 10 years, I’d hate to change it, but how can I trust someone who lies?

    Now, I obviously don’t read crazy anti-vax ramblings – in fact, just seeing “vaccinosis” on a page makes me stop reading immediately. But really, having a vet that you trust deliberately tell you lies makes one wonder if you can trust anybody. I am sufficiently informed not to fall for the alternative nonsense, but others who aren’t just may.

  4. L says:

    I have found a lemon here and there too. Just ask around, make an appointment with a new one in your area. It is like any other relationship, sometimes it works and sometimes it doesn’t. Sometimes it works for a while and then it doesn’t.
    Just my opinion.

  5. kitty says:

    Thanks, the trouble is – this is a 24 hour clinic with specialists and after hours care, so even if I switch, I’d need to come back in case of emergency. Switching to another vet in the same clinic might be a possibility, but is a little awkward. Anyway, sorry for getting off topic.

  6. v.t. says:

    Switching to another vet in the same clinic is only awkward for a very short time. 🙂

    If you’re switching vets, it’s because you want the best care for your pets, you’re not looking for a new best friend. Both that vet and a new vet have had clients with preferences, so don’t let that prohibit you from seeing who you trust.

  7. kitty says:

    Thank you. I keep wondering if she could’ve made an honest mistake somehow or misinterpreted something someone said and not a purposeful lie. As a lie it would’ve been just too stupid and easily verifiable. Anyway, I have almost a year to decide.

  8. v.t. says:

    It could depend on when she actually told you that (new treatments, vaccines, etc sometimes have a margin of doubt in the first years until enough evidence and data are collected to make informed choices) – it could also simply be her personal opinion based on where she obtained her information. Either way, it’s you making the ultimate decisions for your pets, thankfully you have access to reliable information 🙂

  9. kitty says:

    Thank you, something to think about for the next few months. I usually like to give people benefit of the doubt and I have time. Really appreciate the replies.

  10. Mallory says:

    You know, there’s absolutely no scientific study that proves vaccines were ever effective or that they erradicated any disease. I find it ironic that you pick apart holistic approaches but can live with yourself on the vaccine theory, which never worked. If you have any links to any REAL scientific studies that vaccines ever worked, please be sure and email me.

  11. skeptvet says:

    Actually, that’s completely false. The evidence is overwhelming that vaccines have dramatically reduced the suffering and death caused by infectious disease, have eliminated smallpox entirely, and will have eliminated polio within the next decade is overwhelming. The fact that you can make a statement like this illustrates only how far removed your views are from reality.

    While you may not care about the evidence, here are a few examples for those who do:

    Vaccines Greatly Reduce Death, Disability, and Inequity Worldwide

    Evidence for Vaccine Efficacy

    Vaccine Work

    Vaccine Effectiveness

    “Vaccines Don’t Work:” Intellectual Dishonesty at its most Naked

  12. Rochelle Campbell says:

    I am looking into the best method of vaccinating/ protecting our (neutered, small breed) dog and came across this PubMed study. The conclusion, based on a study of over one million dogs, is:

    “Young adult small-breed neutered dogs that received multiple vaccines per office visit were at greatest risk of a VAAE (vaccine-associated adverse events) within 72 hours after vaccination. These factors should be considered in risk assessment and risk communication with clients regarding vaccination.”

    And it specifically notes: “The VAAE rate decreased significantly as body weight increased.” That seems to indicate that some smaller dog breeds’ bodies struggle, for whatever reason (potentially the added adjuvants, metabolic issues more prevalent in smaller breeds?), with the standard one-size-fits- all dosage amount. I’m interested in your thoughts.

    https://www.ncbi.nlm.nih.gov/pubmed/16220670

    Kind regards,
    Rochelle

  13. skeptvet says:

    I have discussed this study before. What it shows is that multiple separate vaccines given together increase the risk of hypersensitivity reactions in small breed dogs. That is why I recommend giving individual vaccines at separate visits for these breeds. However, this is a different issue from the quantity of antigen in individual vaccines or the volume of vaccine necessary to generate an effective immune response. There is still no evidence that reducing the volume of an individual vaccine or the amount of antigen in an individual vaccine will provide effective immunization while reducing adverse reactions. If this is demonstrated through goo quality research, then of course we should alter the vaccines and vaccination practices accordingly. But doing so without this evidence puts dogs at risk without any reason to believe they benefit.

  14. Ann says:

    Where is the evidence that a 2-3 pound dog requires the same volume of vaccination as a 20-150 lb dog? Site specific research.

    Where is the evidence/research that dogs need annual rabies vaccinations or any of the other vaccinations.

  15. skeptvet says:

    The evidence for the duration of immunity for various vaccines is discussed in detail in the AAHA Vaccine Guidelines. Many do not need to be given annually, though a few do, and this depends on the type of vaccine, the nature of the disease, and other factors.

    As for the minimum immunizing dose of antigen, I’ve explained why that does not vary much with body size, and has little to do with the volume of vaccine injected. Your question is unanswerable because it is based on a simplistic and erroneous understanding of how vaccines work.

  16. Nature Lover says:

    To Skeptvet – I just posted a comment for review, but I did not state one section clearly/accurately (regarding autoimmune/diabetes as a reportedly higher incidence in smaller breeds.) Although my sources included these diseases as R/T vaccines in smaller dogs. my statement is not accurate, since larger dogs also develop autoimmune diseases/diabetes. Instead of clarifying this, I should just remove that segment of my comment. If you decide to post my comment, please post this revised version. Thank you.
    Thank you, Ann, for asking the logical, obvious questions, considering the evidence that smaller dogs experience more adverse reactions to vaccines. As for the unfortunate comment by “v.t.” about pet owners “drooling” – I certainly hope that “v.t” does not stand for “veterinarian.” Comment was neither clever nor funny, especially to those who have witnessed devastating effects of vaccinations on a small. beloved pet. Such condescending expressions of contempt should be kept to oneself. Keep it respectful.

  17. Kathy Rosenberger says:

    Based on the lack of evidence on the half-dose theory, I think it makes more sense to only give one vaccine at a time and not vaccinate as often–do titers instead.

  18. skeptvet says:

    I don’t see any reason that this approach is safer or better than the current guidelines, which are based on goo evidence.

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