A closer look at rabies virus vaccination

September 30, 2013 

Recently, a “Letter to the Editor” appeared in The Modesto Bee concerning vaccination. Specifically, the writer was questioning how a pet caretaker is to truly know their companion is protected against a particular disease by vaccination. Rabies vaccination was the main subject.

First off the writer has a valid concern. How do we know our companions are protected from rabies virus because they are vaccinated? Let’s delve into this a bit specifically concerning rabies vaccination.

A vaccine is a substance, usually injected into a patient, to stimulate the immune system to produce antibodies to a specific pathogenic organism. In the case of a rabies vaccination, the substance used is a nonviable form of the actual virus itself. When it is introduced into a dog or cat’s body via injection, the immune system then goes to work creating molecules called antibodies which recognize the viral particles as foreign invaders.

Once the patient’s immune system has produced the specific antibodies to the rabies virus, it is then ready for a potential challenge from an active rabies virus exposure. This comes when a rabid animal contacts the vaccinated patient. Because that patient already has antibodies in their system against the rabies virus from previous vaccination, the immune system goes to work and the invading virus is destroyed. But, as the writer questioned, how do we know the patient is truly protected?

Rabies virus and associated vaccines against it have been widely studied in veterinary medicine I think primarily because of the potential for human exposure. Rabies is a fatal disease in domestic animals and also in humans. There is treatment available with human exposure however this is not the case in our companions.

Adequate protection from rabies virus as mentioned above is obtained by the stimulation of antibody production by the immune system against the rabies virus. This can be measured using a blood test to check the level of circulating antibodies in the bloodstream against the rabies virus. This level is called a titer. Adequate levels of antibodies, a high enough titer, means protection from the rabies virus. Do we need to do this on every patient vaccinated against rabies? The answer is no.

Because of the tremendous amount of research done with rabies vaccination and resultant antibody levels achieved, and I am referencing dogs and cats here, there is little need to check vaccination response by measuring antibody titers against the virus. The vaccination has been proven over and over to produce adequate immunity.

There are cases where rabies titers are required by certain government entities before a dog or cat is allowed into these places. This is because there is no rabies virus in these locations and they want to keep it that way. This is, however, not the case on a routine basis.

That said, there are cases of vaccination failure. In the case of rabies vaccination, the failure rate is so infinitesimally small that we can feel very confident that proper vaccination against rabies will provide adequate protection against the virus if the patient is exposed.

Jeff Kahler is a veterinarian in Modesto. Questions can be submitted to Your Pet in care of LifeStyles, The Modesto Bee, P.O. Box 5256, Modesto 95352

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