Concerns about vaccine safety and questions about the necessity for annual vaccinations have sparked a debate. Dog breeders and owners want to adequately protect their dogs from disease, but they also want to avoid vaccinating more than necessary. Meanwhile, until now, little research has been conducted on duration of vaccination immunity.
The current vaccination schedule for adult dogs calls for administration of four core vaccines (see "Canine Core Vaccines" on page 2). Core vaccines are those recommended for all dogs. Three of these - parvovirus, distemper and adenovirus - are given annually. State law determines the frequency of administration of the rabies vaccine, but it generally ranges from one to three years.
Of the four core vaccines, only rabies is tested routinely to determine its minimum duration of immunity. Most experts agree that the key is to understand which vaccines need to be given annually. Adverse effects from immunizations make this important.
A study under way at Auburn University in Alabama is looking at core-vaccine induced immunity. Though data still is being collected, making it premature to predict recommendations, lead investigator Philip Mansfield, DVM., associate professor of medicine, says, "A protective immune response, depending on the antigen, may persist for several years following vaccination.
"Our goal is to determine the minimal dose of vaccines necessary to immunize puppies and to maintain protection in adulthood. We also hope to learn whether annual revaccination of adult dogs is essential for prevention of infectious disease."
Though no perfect vaccine exists, it is important that a vaccine protects a dog from developing clinical signs after being exposed to infection.(1) Clearly the most important benefit of low-cost, highly effective vaccines is the prevention of disease. Before parvovirus vaccine was available,
the disease claimed countless young puppies. Similar incidents occurred with distemper, hepatitis and rabies.
Vaccinations are of paramount importance in breeding kennels, where population density and the opportunity for exposure to other dogs are among the most critical issues.' Puppies particularly are at substantially higher risk of infection than pet dogs living in houses with one or two other dogs.' To help reduce the risk of spreading diseases, kennels should practice stringent hygiene, follow a vaccination schedule and prevent puppies from having contact with infected dogs.
Concerns about the relationship between vaccinations and adverse side effects are based on reports of illness. Allergic reactions caused by vaccines are well known, Mansfield says. Local reactions might include facial swelling, hives and itching. Swelling, irritation, hair loss and/or color change of hair at the site of the injection also are observed.
Signs of a generalized reaction include restlessness, vomiting, diarrhea, urination, labored breathing and collapse. Other adverse effects may include pain, soreness, stiffness and/or lethargy. Adverse reactions may occur within minutes to days following vaccination.
Most adverse side reactions are immune-mediated. "Because immune-mediated reactions are genetically determined, some breeds – especially certain families of dogs are at increased risk of adverse reactions," Mansfield says. Among breeds that appear to have increased risk are: miniature dachshunds, West Highland white terriers, Old English sheepdogs, Akitas and Weimaraners. Dogs with coat-color dilutions, such as double dilute Shetland sheepdogs and harlequin Great Danes, also are vulnerable.
Concerns about adverse vaccine reactions have intensified to the point that some owners have stopped vaccinating their dogs. "They offer as justification the belief that current vaccines are dangerous and are quick to point out that without vaccines their dogs remain healthy," Mansfield says. "What those individuals fail to realize is that the spread of disease to unvaccinated dogs is prevented by the high percentage of responsible owners who do vaccinate their dogs."
Parvovirus, distemper and adenovirus are recommended in a multi-component vaccine beginning when a puppy is 6 to 8 weeks old. Two repeated vaccinations are given at 10 to 12 weeks and 14 to 16 weeks old. Puppies should receive a rabies immunization at 12 weeks old, and then state laws determine frequency of adult boosters, which range from one to three years. Parvovirus, distemper and adenovirus vaccines routinely are administered annually to adult dogs.
"The most important aspect of a puppy vaccination program is to make certain that the last dose in the core series is administered when the puppy is at least 12 to 14 weeks old," Mansfield says. "Failure to vaccinate a puppy at an age when maternal antibody protection has declined sufficiently - around 12 weeks - will increase a dog's risk."
Among the most significant changes anticipated in the future is a recommendation to discontinue annual booster vaccinations to adult dogs.(2)
The incidence of canine distemper, parvovirus and adenovirus is nearly nonexistent among vaccinated adults, and protection from immunization may be sustained for periods as long as five or six years.(2) Future vaccination standards for adult dogs are likely to center around vaccination intervals of every three years.(2)
Core Vaccine Investigation
The Auburn vaccination study led by Mansfield involves 152 dogs, 30 of which were puppies when the study began. In its fourth year, the study, which is funded by the American Kennel Club Canine Health Foundation, has entailed collection of blood from puppies for the measurement of antibody levels before their first vaccination and two weeks following the second vaccination.
"Puppies with antibody levels sufficient to protect them against viruses required no additional vaccines in the initial series," Mansfield says. "All dogs in our study are tested annually for three consecutive years and additional vaccines are given only as necessary to sustain immunity."
Though most dogs develop an average immune response, a small proportion has a poor immune response and may not be protected against infection despite vaccination.(3) Dogs with a depressed immune response - those with heavy parasite infestations or are malnourished or stressed - may not respond well to vaccines. Stress could include pregnancy, fatigue and malnourishment.
The practice of administering vaccines in multicomponent, or multivalent, vaccines also may hinder a normal response to vaccines. Parvovirus, distemper and adenovirus often are given in a combination vaccine that includes parainfluenza, one of the main causes of kennel cough. When multiple vaccines are given, there is competition at the antigen-presenting cell level.(4)
A new clinical test recently developed that measures distemper, parvovirus and adenovirus is expected to
help determine when vaccines are needed. "When this test is available, we may be able to reduce the number of multiple vaccinations to puppies and determine specifically when an adult dog needs revaccination," Mansfield says.
A question dog owners sometimes ask is whether toy and small-breed dogs need the same vaccine dosage as medium-, large- and giant-sized dogs to receive protection. "The answer is yes” Mansfield says. "When a vaccine is administered, you are introducing you are introducing an organism to a dog's immune system. The dosage should be same; it is not the same as giving an antibiotic or other medication."
Though it is premature to know whether the recommended vaccination schedule for dogs is going to change, vaccine safety should be the main concern. "It is reasonable to avoid using unnecessary vaccines and to vaccinate no more than necessary to provide essential protection against infectious agents," Mansfield says. "The solution to the vaccine controversy is not to abandon vaccination as an effective means of disease prevention and control. The benefits of vaccines far outweigh the risk of adverse reactions."
1. Van Oirschot J1 Efficacy and Safety of Vaccines, The Veterinary Quarterly, 1994; 16:1, p. 7S,
2. Ford RB, Schultz RD. Vaccines and Vaccinations: Issues for the 21st Century, Kirk's Current Veterinary Therapy XII Small Animal Practice, WB. Saunders Company, Philadelphia. 2000; p, 250.
3. Tizard IR. An Introduction to Veterinary Immunology, WB. Saunders Company, Philadelphia. 1977; p. 178.
4. Smith CA, Current Concepts: Are we vaccinating too much? Journal of the American Veterinary Medical Association. 1995; 207:4
As printed in the Purina Pro Club Review - January 2002
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