(The following article is made available through the USKBTC’s participation in AKC’s Canine Health Foundation Conference in St. Louis. USKBTC’s Health & Genetics Chairman, Gene Possidento attended the conference in September 2003.)
Vaccine Update: Controversial Issues
Author: Saralyn Smith-Carr, DVM, PhD, DACVIM; Jim Wright, DVM, PhD, DACVPM
Many controversial issues surround the use of vaccines in the dog and cat. New vaccine technology has let to an increase in the number of vaccines available for prevention of infectious disease in susceptible pets. However, risk of disease rather than availability should be considered when determining which vaccines are used in a vaccination program. Uncertainty arises concerning the designation of vaccines that should be used in a vaccine program and the method of individualizing the vaccine program for each pet. The American Veterinary Medical Association has designated core and non-core vaccines for dogs and cats to provide guidance to the veterinary practitioner. Core vaccines are those needed by all cats and dogs while non-core vaccines are recommended based on increased risk of exposure to an infectious agent.
An assortment of vaccines are available that are in both core and non-core vaccine categories. Therefore, the type4 of vaccine that is administered is also an issue of divergence. The types of vaccines available are modified live virus, killed virus or bacteria, subunit, and recombinant virus. Veterinarians as health-care givers must be conscious of when to choose modified live, subunit, killed or recombinant vaccines for incorporation into the vaccine program for each individual pet. Reasons for choice of a particular vaccine are efficacy, availability and avoidance of predictable adverse vaccine reactions such as abortion caused by administering live virus vaccines to pregnant animals.
Unpredictable adverse reactions to vaccines are another problem that both pet owners and veterinarians face today. Most adverse reactions such as hypersensitivity reactions can be successfully treated or minor reactions such as soreness, fever and lethargy disappear within a day without treatment. More severe adverse reactions occur that are linked to recent vaccination of the pet. Injection-site sarcomas and autoimmune disease are two such adverse reactions linked to vaccine administration that may lead to the death of the animal. Injection-site sarcomas in cats became a problem with the advent of feline leukemia virus vaccine, a subunit vaccine, and rabies vaccine, a killed virus vaccine that contain an aluminum-based adjuvant. Adjuvants are used in vaccine formulation to boost the immune response to the vaccine proteins (antigens). Hypersensitivity reactions leading to urticaria and wheal formation have been associated with the leptospira bacterin. Therefore adverse reactions are an important consideration in vaccine selection.
Vaccine programs along with improved sanitation have been very beneficial in the prevention of transmission and spread of severe infectious diseases. Therefore the abandonment of these programs would be neither wise nor advised. A better approach would be to evaluate how often a vaccine should be administered. This would decrease the frequency of vaccines that potentially lead to adverse reactions. Yearly vaccinations have been the standard of health in the past; however, with the development of the; more advanced vaccines, protection may last longer. Therefore the issue of controversy is duration of immunity of core vaccines.
Reports from the veterinary investigators have indicated that the duration of immunity of the core vaccines are longer than one year. These same investigators have expressed the view that all canine core vaccines except rabies should be administered every three years instead of yearly. We decided to conduct our own investigation into the duration of immunity of three of the core vaccines recommended for dogs, canine adenovirus, canine distemper virus, and canine parvovirus vaccines.