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Question: Why do I need to keep vaccinating my pet? Do vaccines last longer than the vet clinic recommends?
I have been asked this question several times over the last year, so I thought I’d address it here. However, I’ll be completely honest up-front: this is not an easy topic. I’ll breakdown the article into a couple sections to make things easier. The first section will cover dog vaccines, namely the “Base” vaccine, the Rabies vaccine, and a few other vaccines available for dogs. I’ll also discuss vaccine schedules and whether the immunity from these vaccines last longer than first thought, and whether this immunity can be tested. The final section will cover vaccines in cats as well.
I’d like to first give the consensus opinion in the veterinary/scientific field that vaccines are incredibly important. They protect against preventable, major diseases which at best could cause serious health problems, and at worse can be fatal.
BASE VACCINE IN DOGS
The “Base” vaccine covers 4 major diseases in dogs: Parvovirus, Distemper virus, Parainfluenza, and Adenovirus (which can cause liver disease in dogs). In the late 1990s and early 2000s the American Veterinary Medical Association (AVMA), the American Animal Hospital Association (AAHA), and the American Association of Feline Practitioners (AAFP), released new guidelines in regards to vaccine schedules, which were adopted by the Canadian Veterinary Medical Association.
The Base vaccine is recommended as a monthly vaccine for puppies between the age of 6 and 16 weeks, a booster vaccine 1 year later, then re-vaccination every 3 years. Prior to these revised guidelines, vaccines were given yearly, regardless of the vaccine or the patient’s needs.
Now, on to the questions :
Can the Base vaccine last longer than 3 years, after the 1 year booster?
Short answer: Yes*, maybe.
Can my dog’s immunity be measured?
Short answer : Yes*, sort of.
*There are some caveats with theses answers, because things are never so simple in medicine. So here’s the long answer:
Titer testing is the act of testing a blood sample to measure the amount of antibodies available to ensure immunity against a particular disease. In theory, a veterinarian could submit a blood sample for titer testing to determine if there are enough antibodies for the immune system to overcome exposure to particular disease, instead of re-vaccinating automatically. In fact, several studies demonstrated that the Base vaccine could cause antibody levels to maintain immunity levels for between 1 to 7 years post-vaccination. The variation in antibody levels can be attributed to individual immune systems, the type of vaccines used, presence of underlying disease not known at time of vaccination, and many, many other factors.
Unfortunately, I can see 2 problems with titer testing for the base vaccine: price and repetition. Titer tests can easily be 3-5 times more expensive than the cost of vaccination itself and it must be repeated every 6-12 months, with re-vaccination theoretically happening after antibody levels drop to below a reference point.
Furthermore, while titer testing can measure antibody level, it can’t measure cell-mediated immunity, which is the body’s real protection against a disease. To my knowledge, cell-mediated immunity isn’t measurable.
RABIES VACCINE
The Rabies vaccine example gives us further example of the limitations of titer tests. Rabies vaccine schedule guidelines are for a single vaccination after 14-16 weeks of age, a booster 1 year later, then re-vaccination every 3 years. Once again, it is possible for the vaccine to theoretically last longer than the 3 year recommendation.
Titer testing for immunity against rabies is mandatory for travel to non-endemic countries (where rabies isn’t present in the natural environment), such as Australia, New Zealand and United Kingdom. In this situation, titer testing can only ensure that an animal has been previously vaccinated against rabies, since it is unlikely that a pet has developed antibodies against this disease through exposure. For anyone who has travelled to non-endemic destinations, you know first-hand that this doesn’t stop these countries from imposing sometimes extensive quarantine protocols for incoming pets, even with high titer levels. High titers does not correlate to active protection.
In practice, I consider the Rabies vaccine to be more of a legal issue, than a medical one. Although I’m not here to enforce municipal, provincial or federal policies, it IS my job to inform my clients of potential issues faced with non-vaccination. If a pet bites someone, the animal could be quarantined for several weeks, or even euthanized and tested for live rabies virus, if its vaccines are not up to date. Titers cannot be used as proof of immunity in this situation. Rabies is also fatal, and transmissible to humans, therefore it is not a disease to take lightly.
LEPTOSPIROSIS VACCINE
The leptospirosis vaccine protects against a bacteria found in stagnant water and spread commonly by the urine of infected wild animals. The schedule for this vaccine is : monthly vaccination as a puppy until 14-16 weeks of age (2 total), and then yearly re-vaccination. Now I know what you’re thinking, why isn’t this vaccine given every 3 years like the base or the rabies vaccines ? Well, antibody levels and cell-mediated immunity can vary depending on the type of vaccine given. I could write a whole book on how vaccines trigger the immune system, and the different types of antibodies, but I’d much rather not! But a recent study showed that most dogs were negative for antibodies against leptospirosis 1 year after vaccination. Unfortunately, this vaccine just doesn’t trigger the same response as other vaccines.
FELINE VACCINES
The base vaccine for cats protect against Panleukopenia virus, Calicivirus, and Rhinotracheitis virus. It is given on the same schedule as the dog base vaccine: monthly vaccine for kittens with the last vaccine given between 14 and 16 weeks of age (or later), a booster vaccine 1 year later, then re-vaccination every 3 years. The AAFP Feline Vaccination Advisory Panel Report states: “Because antibody titers may not reliably correlate with, or predict, the degree of protection or susceptibility for an individual cat, the Advisory Panel recommends employing defined revaccination intervals rather than measuring antibody titers to assure protection”. It was determined in several studies that titer levels did not correlate to protective immunity against these viruses and therefore, titer testing isn’t recommended for cats.
I hope this overview of vaccines was informative. It is possible that in the future it is determined that the core vaccines mentioned in this article may be given on longer re-vaccination intervals, but for now, there is not a reliable method to measure whether an animal is adequately protected against the diseases longer than the set re-vaccination schedule. We have yet to determine the role of cell-mediated immunity in disease prevention. Antibody titers do correlate with protection to a degree; however, are not indicative of absolute protection. Better be safe and vaccinate !
If you have any questions, queries, comments, or just feel like telling me how great this column was, you can send any or all of the above to: AskDrJames@outlook.com. All questions used for blogging purposes will remain 100% anonymous.
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