VACCINOLOGY

The subject of vaccines and vaccination protocols has become a hot topic in dog circles over recent years. Concerns have been raised about the increased incidence of immune-mediated diseases such as thromobytopenia (low platelet counts), hemolytic anemia (immune-mediated red blood cell destruction), immune-mediated arthritis and immune mediated skin disease as well as allergic vaccine reactions, seizures and other problems possibly related to vaccination. This discussion will provide some insight into the controversy and hopefully provide a rational approach to vaccination.

The first point that must be made is that the vaccines available today are very effective. Since the advent of vaccination programs in dogs the incidence of canine distemper, rabies, canine hepatitis, parvovirus, and parainfluenza (viral component of the “kennel cough” complex) have been dramatically reduced. When I graduated from veterinary school in 1980 the canine parvovirus epidemic had just begun and hundreds of thousands of dogs died due to lack of an effective vaccine. Now we hardly see a case of parvovirus and when we do it’s in an inadequately vaccinated puppy or adult. Vaccination works by stimulating the immune system respond to a mild dose of the disease-causing virus (modified-live virus vaccine) or killed form of the virus (killed vaccine). It is generally felt that MLV vaccines stimulate better and longer duration of immunity than killed vaccines. In response to the vaccination the immune system generates clones of lymphocytes capable of producing antibodies specific for that disease. Some of these cells are “memory cells” and will produce antibodies on re-exposure to the same disease or to a booster vaccination. Booster vaccination helps to maintain this population of memory cells, which allows a faster response to exposure to the disease later on. The presence of these memory cells and their protein products called antibodies is the basis for the concept of “titers”. Titers are the antibody levels maintained by the memory cells in the blood stream. Over the years scientists have determined the levels of antibody needed to maintain protection against infection by different diseases – protective titers. Ideally, the frequency of vaccination should be based on the protective titer. One concern that has been raised is what constitutes a protective titer. This titer may vary from individual to individual, the age of the animal, stress factors and exposure potential. Some animals can be vaccinated every 2-4 years because they maintain a protective titer for that long. Other individuals require more frequent vaccination intervals. The only way to verify the vaccination interval in a particular animal is to have the titer for a specific disease checked by a blood sample. The problem here is the expense involved to check titers vs. the expense of annual vaccinations. It is less expensive to vaccinate yearly than to check titers so annual vaccinations are recommended. We also vaccinate pets based on exposure potential. Not all pets have tick exposure so vaccinating for Lyme’s disease is not necessary in all cases. Bordetella is the bacterial component of the kennel cough complex and again, not all dogs are at risk. The term “core vaccines” has been used to denote the vaccinations all dogs should have and consist of rabies, canine distemper, canine parvovirus, adenovirus and parainfluenza. Other vaccines, which can be added, based on exposure potential are leptospirosis, bordetella, coronavirus, and Lyme’s.

Vaccine reactions can and do occur although they are infrequent. Acute allergic reactions also known as “anaphylactic reactions” occur within 10-30 minutes of the vaccinations and consist of vomiting, diarrhea, collapse, depression, pale gums all consistent with a shock-like reaction. I consider this a life-threatening reaction and immediate veterinary attention is required. Treatment involves IV fluids, antihistamines, steroids, epinephrine and supportive care. Other reactions occur later (several hours) such as hive-like reactions with itching, swollen muzzle and face, fever, lameness and just not feeling well. These reactions are not considered life-threatening and immediate intervention is seldom necessary. Treatment consists of antihistamines, steroids and/or aspirin.

My current recommendations are to get the core vaccines annually. You certainly have the option of doing titers on a yearly basis and then vaccinate accordingly. Titers are about double or triple the cost of the vaccinations and take about 1-2 weeks to get results from the lab. As the laws are written for the rabies vaccine it would have to be given regardless of the titer. Titers are available for canine distemper and canine parvovirus, which are the major diseases I’m worried about.

The future of vaccines and vaccinations is currently undergoing reevaluation as new information and technology becomes available. Changes are certainly in the near future and one thing we can always be assured of is change.