Our recent article and Press Release on the small adult dog pilot study using a half-dose bivalent vaccine booster has generated lots of comments. We thought it would be useful, therefore, to give readers more specific details regarding the background science and rationale behind the completed pilot study.
There is little doubt that application of modern vaccine technology has permitted us to effectively protect companion animals (and people) against serious infectious diseases. While this benefit is widely recognized, there is a small but real risk of adverse events following vaccinations of any species.
Several factors are known to contribute to the risk of adverse vaccine reactions:
- Genetic predisposition (family history and breed type)
- Influence of sex hormonal change (estrus – menstrual cycle)
- Type of vaccine and adjuvant used (rabies and thimerosol, which is a form of mercury).
Certain breeds or families of dogs appear to be more susceptible to adverse vaccine reactions, particularly post-vaccinal seizures, high fevers, and painful episodes of hypertrophic osteodystrophy (HOD).Therefore, we should advise companion animal breeders and caregivers of the potential for genetically susceptible littermates and relatives to be at increased risk for similar adverse vaccine reactions. In popular (or rare) inbred and line bred animals, the breed in general can be at increased risk, because of the inherited tendency to respond with a bad reaction to viruses or bacteria of a disease they have been vaccinated against.
In these special situations, appropriate alternatives to current canine vaccine practices include: measuring serum antibody titers; avoiding unnecessary vaccines and not vaccinating too often; deferring vaccinations of sick or febrile individuals; tailoring specific minimal vaccination protocol for dogs of breeds or families known to be at increased risk for adverse reactions; starting vaccination series later, such as at 9-10 weeks of age when the immune system is more able to handle challenges; paying particular attention to the puppy’s behavior and overall health after each booster; and, avoiding revaccination of individuals already experiencing significant side effects. Littermates and close relatives of affected puppies should be closely monitored after receiving additional vaccines in a puppy series, as they may be at higher risk.
Duration of Immunity
Vaccination typically provides an immune response that is similar in duration to that following a natural infection.
First, you need to know what acquired (aka adaptive) immunity is. In acquired immunity, pathogen-specific receptors are “acquired” during the lifetime of the organism and the system adapts to handle future challenges. The opposite of that is innate immunity, which means that pathogen-specific receptors are already encoded in the immune system’s germline. The acquired response is called “adaptive” because it prepares the body’s immune system for future challenges. It can be a good thing. When I speak about autoimmunity that is when it is a bad thing as it is then maladaptive.
In general, adaptive immunity to viruses develops earliest and is highly effective. Such anti-viral immune responses often result in the development of sterile immunity. Basically, sterile or sterilizing immunity occurs when an individual is fully protected from becoming re-infected by a particular infectious agent, typically a virus.
Whether this immune response occurs because of natural exposure, with infection followed by recovery, or, whether it is from vaccination, this individual can no longer become infected with this disease agent, but can still shed the agent into the environment for up to 14 days. This immunity often lasts for the rest of their life. Old dogs and cats rarely die from vaccine-preventable infectious disease, especially when they have been vaccinated and immunized as young adults (i.e. between 16 weeks and 1 year of age).
Vaccines that do produce sterile immunity include: distemper virus, adenovirus, and parvovirus in the dog, and panleukopenia virus in the cat.
However, young animals do die, often because vaccines were either not given or not given at an appropriate age (e.g. too early in life in the presence of maternally derived antibody). A recently published study examined how long the immunity lasted for the core viral vaccines in dogs that had not been revaccinated for as long as 9 years. These animals had antibodies against canine distemper virus, canine parvovirus type-2 and canine adenovirus type-2 at levels considered protective and when challenged with these viruses, the dogs did not show infection and/or disease. Thus, even a single dose of modified live virus canine or feline core (against feline parvovirus, feline calicivirus and feline herpesvirus) vaccines, when administered at 16 weeks or older, should provide long-term immunity in a very high percentage of animals, while also increasing the population or “herd” immunity. (Herd immunity happens when the group or “herd” is protected against the disease, even though a few are not vaccinated or protected.)
But, not all vaccines produce sterilizing immunity (where the disease germs they are protected against do not cause disease). This other type of immunity is non-sterile immunity, where some disease germs can still infect them, and they may show signs of disease, but they usually do not show all symptoms of the full-blown disease. Since they can still become re-infected, they are not protected as well as if they had sterile immunity. Examples of vaccines that produce non-sterile immunity would be leptospirosis, bordetella, rabies virus, herpesvirus and calicivirus – the latter two being upper respiratory viruses of cats. While non-sterile immunity may not protect the animal from infection, it should keep the infection from progressing to severe clinical disease.
Interpreting Titer Results
Interpreting titers correctly depends upon the disease in question.
With agents that produce sterile immunity, the presence of any measurable antibody shows protection. The positive titer test result is fairly straightforward – it is positive and for sterile immunity that is all we need to know. A negative titer test result is more difficult to interpret, because a negative titer is not the same thing as a zero titer and it doesn’t necessarily mean that animal is unprotected. A negative result usually means the titer has failed to reach the threshold of providing sterile immunity. This is an important distinction, because for the clinically important distemper and parvovirus diseases of dogs, and panleukopenia of cats, a negative or zero antibody titer indicates that the animal is not protected against canine parvovirus and may not be protected against canine distemper virus or feline panleukopenia virus.
Protection from viral disease as indicated by a positive titer result is not likely to suddenly drop off unless an animal develops a medical problem such as cancer or receives high or prolonged doses of immunosuppressive drugs.
With other agents such as rabies, their titers must reach a certain level to indicate immunity.
So, vaccines based on viruses (e.g. distemper) prompt an immune response that lasts much longer than the immunity from other kinds such as bacterial, parasitic vaccine or killed inactivated vaccines (e.g. rabies). Lumping the 2 kinds of responses together may be why practitioners think titers can suddenly disappear.
Finally, what does more than a decade of experience with vaccine titer testing reveal? Published studies in refereed journals show that 90-98% of dogs and cats that have been properly vaccinated develop good measurable antibody titers to the infectious agent measured. So, in contrast to the concerns of some practitioners, using vaccine titer testing as a means to assess vaccine-induced protection will likely result in the animal avoiding needless and unwise booster vaccinations.
When an adequate immune memory has already been established, there is little reason to introduce unnecessary antigen, adjuvant, and preservatives by administering booster vaccines. By measuring serum antibody titers regularly (many veterinarians recommend annually, although my own recommendation is triennially or more often, if needed), one can assess whether a given animal’s humoral immune response has fallen below levels of adequate immune memory. In that event, an appropriate vaccine booster can be administered.
Other Issues with Over-Vaccination
Other issues arise from over-vaccination, as the increased cost in time and dollars spent needs to be considered, despite the well-intentioned solicitation of clients to encourage annual booster vaccinations so that pets also can receive a wellness examination. Giving annual boosters when they are not necessary is likely to be of little benefit to the pet’s existing level of protection against these infectious diseases. It also increases the risk of adverse reactions from the repeated exposure to foreign substances. However, an annual wellness examination is in the best interest of the pet, so pet owners should not avoid the examination itself.
Compliance or Resistance to Current Vaccine Guidelines
For almost two decades, the issues discussed above on over-vaccination and vaccine safety for companion and livestock animals have been raised by immunologists and veterinary clinicians. But, how has this still controversial knowledge impacted the veterinary profession and animal owner today? Have veterinarians really embraced the national policies on vaccination guidelines? Does the public trust veterinarians to be up-to-date on these issues or are they unsure? Do they believe veterinarians have a conflict of
interest if they seek the income from annual booster vaccinations? Given media information regarding human autism and measles vaccination, the public is more aware and worried about vaccine safety.
Claims that there is no scientific evidence linking vaccinations with adverse effects and serious illness is misinformation that ignores research and that can be confusing. On the other hand, anti-vaccine zealots also give out misinformation which ignores research. Neither of these polarized views is helpful.
Treatment of Vaccinosis
As the diagnosis of vaccinosis is an exclusionary one – i.e. typically, nothing will be found upon other testing to explain the symptoms, therapy is based upon alleviating any symptoms. Oral homeopathics can be used such as Thuja (for all vaccines other than rabies), and Lyssin to help detoxify the rabies molecular energy (“miasm”). If there are no holistic veterinarians in the area, these homeopathics may be available from human alternative or homeopathic pharmacies.
Conventional therapy typically uses steroids in tapering doses over 4-6 weeks to stop the inflammatory process and clinical symptoms. Therapy begins with an injection of dexamethasone phosphate first, and if the animal improves right away, is continued with prednisone at 0.5 mg per pound twice daily for 5-7 days, then tapered gradually over the next month to every other day. The use of steroids will cause an increase in water intake and urination, but the animal should be able to handle the drug at these tapering doses for a few weeks. If a holistic veterinarian wants to try an alternative therapy to steroids, with homeopathic remedies and nutraceuticals, this approach can also work.
Much still needs to be standardized and individualized, where appropriate, to ensure the safety and efficacy of veterinary vaccines. There remains controversy, failure to comply with current national vaccine policies and guidelines, resistance to change, and denial of adverse events within the general veterinary community as well as within society as a whole.
ADDITIONAL INFORMATION ON SMALL ADULT DOG VACCINE PILOT STUDY
Some readers have wondered why we didn’t perform this study in unvaccinated puppies or unvaccinated adults. We considered it to be unethical to select unvaccinated dogs because we couldn’t be sure they would be protected – even though we believed they would be, based upon prior clinical experience. If our hypothesis was wrong, they would be at risk for contracting canine parvovirus or distemper diseases.
Another expressed concern was whether measuring serum antibody titers against these two viral diseases would accurately predict protection and, if so, for what duration? Actually, the published scientific literature documents that for the viruses that produce
sterile immunity in immunized animals, namely, canine distemper, canine parvovirus, canine adenovirus-2 and feline panleukopenia virus, protection is predicted by the presence of adequate serum antibody titers. This protection should prevent them from being subsequently infected by these viruses and should essentially be lifelong.
Finally, a pilot study is a small scale initial study conducted to assess outcomes and improve upon the study design, if needed, prior to performance of a full-scale research project. It is unlikely that anyone would undertake a much larger similar study, as the vaccine industry wouldn’t want it and recruiting and expecting participants to continue for 6 months is often difficult. One would need to enroll 50% more cases than needed to expect a completed case cohort of enough dogs at the end. Even with the convincing results of the current pilot study, changes in current vaccine guidelines would likely take years to implement.
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