By Tracie Korol
How can we vaccinate our dogs enough, but not too much?
The best tool for this is called a vaccine or antibody titer test. It measures the levels of a specific antibody in a dog’s blood. Sounds great! A test I can run every year to see if my dog’s immunity has gotten low and needs boosting! It seems like the perfect solution to worries about over-vaccination.
However appealing that idea might be, titer tests can’t be used in this way. That’s because your dog’s immune system is not a gas tank, vaccines are not gas pumps, and titer tests are not gas gauges.
A “titer” is a measurement of how much antibody to a certain virus (or other antigen) is circulating in the blood at that moment. Titers are usually expressed in a ratio, which is how many times they could dilute the blood before they couldn’t find antibodies anymore. If the lab was able to dilute it two times, and then didn’t find any more antibodies, that would be expressed as a titer of 1:2. If they could dilute it a thousand times before they couldn’t find any antibodies, which would be a titer of 1:1000.
It would be wonderful to say that once this ratio dips below a certain level, it’s time to give another vaccination to “boost” immunity. But that reflects an incorrect understanding of the immune response. Vaccines don’t inject immunity into a dog. Instead, they stimulate the immune system to form two kinds of cells, antibodies that fight the current infection, and memory cells that remain behind after the infection has been eradicated, to pump out more antibodies if the same virus is encountered in the future.
Memory cells persist for 20 years or more, and are not increased when the animal is re-vaccinated or re-exposed to the disease. The detection of antibodies in the bloodstream, which is what a titer test does, tells us that process took place and that memory cells are present, but the absence of antibodies does not mean there are no memory cells or that the dog is not immune. Veterinary immunologist Ian Tizard writes, “You can have a negative titer and if the pet is exposed, memory cells can respond within hours to regenerate enough antibodies for protective immunity.” (Tizard, Ian R., Veterinary Immunology: An Introduction, 6th Ed, Saunders 2000.)
You cannot make an immune dog more immune to a virus with additional vaccination as the previous immunity will wipe out the virus in the vaccine. With yearly boosters there will be no increase in immunity and consequently, no benefit to the dog. So, if you can’t top off your dog’s immunity to viruses with booster shots, and you can’t tell for sure from the titer test if his or her immunity is waning, what could a titer test possibly be good for?
It is another tool in your Healthy Dog tool kit. Most veterinarians, unless prompted by a client, will assume you’re there for “the usual” and will vaccinate every year without considering the general health of the animal or its lifestyle. (If your teacup pet never leaves the patio, its chances of contracting a major disease are slim. That’s lifestyle.) It is up to you to educate yourself and advocate for your dog, know what vaccines and tests might benefit him. A titer can help you gather more information.
Note: Several companies launched in-office, core-titer test kits in early 2011 that are being used in various clinics in Savannah and Charleston.
To date, by sample, these tests are not available locally.
