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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