To vaccinate, or not to vaccinate. That is the question.
For decades, many decades, veterinarians have been recommending dogs and cats be vaccinated annually for life. A relative few years ago veterinarians began following the advice of some experts, telling pet owners that vaccines would continue to protect their pets for two, three or even more years.
More than a few veterinarians said, “Show me the beef,” or at least its laboratory equivalent, “Show me the actual protection.”
As a result, according to Dr. Richard Ford, a board-certified internist who recently wrote in Today’s Veterinary Practice, “As demand for vaccine titers increased, veterinary laboratories began offering antibody titer panels for dogs and cats while two companies developed in-clinic antibody tests.”
Veterinarians naturally began asking the pertinent question, “What, exactly, do the results of these titer tests mean?”
First, a definition. Titer comes from the French word, titre, meaning, “to make a standard.” Dorland’s Medical Dictionary defines it as “quantity of a substance required to produce a reaction with a given volume of another substance, or, the amount of one substance required to correspond with a given amount of another substance.” Sound like a lot of gobbledygook? Here it is in plain English: If a titer is zero, the body’s immune system has not responded to either vaccine or disease. From there, a reading from “just above zero” to “a whole bunch” indicates the immune system has responded, and “a whole bunch” is a stronger response than just above zero.
However most of these vaccine “titers” are not really titers at all. They are just “positive” or “negative.” A true titer gives a reading, a ratio, a number, from a little to a lot. Which puts us right back where we started: what does it mean? Perhaps more than you might think.
“Positive” has been defined for each test to correlate to the gold standard, which is laboratory testing for an antibody level to actually kill virus in a Petri dish or test tube. HI, or hemagglutination inhibition is another test of immune-system strength.
“Negative” may mean that the pet is unprotected, although complexities in the mammalian immune system mean that the antibody being measured by the test is low, when CMI, or cell-mediated immunity may still be able to respond if the pet is exposed to disease.
As Simple As PIE. Not.
PIE stands for Protection, Infection and Exposure. A positive test might mean that the pet has Protection from vaccination, but the antibodies the test looks for could just as easily mean the immune system is responding because the patient is Infected with the disease the test is designed to detect. E stands for Exposure, representing the state of the pet having been exposed to the disease, surviving it, and the remaining antibody response may not mean the pet is protected.
Ultimately, Dr. Ford says, “The only true test of protective immunity involves exposure (challenge) to a virulent pathogen…” This is the standard test vaccines must pass in order to be licensed: A vaccinated laboratory dog must not only live when its vaccination is challenged by disease-causing pathogen, it must also not become ill. Who among us wants his beloved pet exposed to potentially deadly diseases to find out whether he is protected? As for me, I will simply vaccinate our pets annually. The other option is to test periodically, in accordance with your pet’s doctor’s recommended interval.
Is One Test Enough?
Keep in mind, too, that not every disease we vaccinate our pets for has a test.
There is a blood test for Rabies vaccination response, but no states allow the result to take the place of annual or triennial vaccination against Rabies. State laws vary.
Available Tests For Dogs:
Distemper, Parvovirus and Adenovirus (hepatitis and upper respiratory disease) in-clinic and laboratory tests are considered reliable for both vaccine response and disease protection.
Canine Influenza, Bordetella, have no commercially-available tests to determine level of protection.
Available Tests For Cats:
Calicivirus disease correlation between gold-standard laboratory testing and protection is described in Dr. Ford’s article as “fair to good.”
Herpesvirus disease correlation between gold-standard laboratory testing and protection is described as “only fair.”
Panleukopenia in-clinic and laboratory tests are considered reliable for both vaccine response and disease protection.
By no means is this article intended to be exhaustive on the subject of vaccination vs. laboratory testing, rather, it is intended to educate the pet owner with a foundation on the subject.
See you next week, Dr. Randolph.