Vaccine Titer Tests: What They Can and Can’t Do

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One of the tests I asked for at Otto’s annual wellness exam last week was a vaccine titer test. These blood tests are able to detect antibodies that the dog has produced in response to a vaccination. Such positive results can confirm that the dog responded in the desired manner to the vaccination and is now protected against the diseases he was vaccinated for.

However, many of us owners who ask (and pay) for titer tests year after year are not doing this to assure themselves that their dogs are protected against disease. In my case (and that of many of my friends), we are paying $50 to $100 a year for the test to prove to our veterinarians that our dogs are adequately protected against disease – to ward off the overzealous promotion of what we know to be unneeded (and thus excessive) vaccinations. Because once we have the first positive titer test results, it’s almost certain that he is protected for life from the diseases he was vaccinated for. The only exceptions to this are rare.

I adopted Otto from a shelter in June 2008. He was picked up as a stray two months prior, and was estimated to be about 7-8 months old. During his two-month stay in the shelter, he had received four combination vaccinations (for distemper, adenovirus Type-2, coronavirus, parainfluenza, and parvovirus); another vaccination for adenovirus type 2 (combined with parainfluenza and bordetella); and a rabies vaccine. The only vaccines he’s received since then are rabies vaccines: a 3-year vaccine given in April 2009, and another one given in late March 2012.

I brought Otto to a local veterinarian in spring of 2010 for a heartworm test and wellness exam. The vet was adamant that Otto also needed “booster” vaccines. The vet had been recommended to me as the best one in my town, so this was a bit discouraging. (So-called “boosters” do not, in fact, “boost” immunity. If the dog has wither circulating antibodies against disease OR immune “memory cells” — cell-mediated immunity that has developed following a vaccine against or infection from the disease — he’s got as much immunity as he CAN have against those diseases.) I asked the veterinarian if he would be content with the results of a vaccine titer test; if the test showed that Otto still had circulating antibodies to the vaccines he had received at the shelter, would he be satisfied that Otto did not need further vaccines? He said he would. So I paid for a titer test, which came back, as I expected, with a nice healthy positive result.

In spring 2011, however, I received a postcard from that veterinarian’s office suggesting that Otto was not just “due” but “OVERDUE” for a laundry list of vaccines. So this was going to be an annual argument, it looked like. I strongly believe in annual wellness examinations and blood tests, but I don’t think my healthy dog need to be vaccinated with anything but the state-required rabies vaccine again. I decided to seek out a new veterinarian – someone younger and, I hoped, more comfortable with the idea that Otto’s previous vaccinations and apparent good health meant he wouldn’t need further vaccinations for years, if ever!

I found a highly recommended veterinarian the next town over, a college town with a lot of progressive, younger doctors. He agreed that Otto was probably protected by his previous vaccines – but wanted to repeat the titer test to “prove” this. I figured if it helped him feel more comfortable NOT recommending further vaccines, it would be a small price to pay to have access to this larger, better equipped, more modern clinic. We ran another titer test; nice and positive. Otto and later Tito saw the same vet later in the year for unrelated issues, and I was mostly pleased with those experiences.

In spring 2012, when I made an appointment at this clinic for Otto’s annual wellness visit and a heartworm test, despite requesting the vet who saw Otto the previous year, I was given an appointment with one of the (older) practice owners. And she wanted to talk to me about vaccines. She felt strongly that a positive result to a titer test was not enough to prove that Otto was protected against disease. She told me that dogs whose titer tests reveal circulating antibodies may lack cell-mediated immunity (adequate T-cells) and be unable to defend themselves against illness. I have heard that, I responded, “but isn’t that rare?” She agreed that it was. “And can’t dogs with past positive titer tests be protected by cell-mediated immunity even if their later titer tests don’t show any circulating antibodies?” I asked. She agreed that this can be true – that previously vaccinated dogs may lack circulating antibodies, but retain immune memory cells that will “remember” experiencing a disease antigen, and mount a vigorous immune response if challenged with disease. But she wanted to stress that there are rare cases where dogs with nice high levels of circulating antibodies but a dysfunctional cell-mediated immune response failed to respond properly to a disease challenge. So her takeaway point was this: You should vaccinate your dog again, regardless of titer test results.

Back to the drawing board — looking for a new vet.

I recently found a young doctor at a clinic in my town. Before I made an appointment for Otto’s annual wellness exam and heartworm test, I asked the practice receptionist if I could have some time to talk to the vet and find out whether he was comfortable with the idea that Otto was not in need of any vaccinations. Later, talking to the vet on the phone, he said he would be willing to accept this – but would feel most comfortable with a current titer test showing a positive antibody result. Well, beggars can’t be choosers. I agreed, and the test came back positive. So far, so good.

It might seem crazy, paying as much as $100 for an unnecessary test annually in an attempt to prove that my dog doesn’t need a $20 vaccination. But I need a local vet who will work with me, happily, without feeling that “overdue vaccines” are putting my dog at risk. I spent 14 years with another dog whose severe allergies may well have been caused and worsened by the completely unnecessary annual vaccines I didn’t know enough to refuse in his first five or six years. I’m not going to risk putting another dog through years of suffering like that to save a few bucks. If the titer test is the price of a good local vet’s cooperation, I’m willing to pay it.

For a very thorough article on canine vaccinations and titer tests, see “Beware of Over-Vaccinating Your Dog“.

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