Canine Vaccinations
October, 1999
Vaccination of animals and people has long been considered an
important component of a complete health program. Both human and
veterinary medicine can boast of successful records in
controlling important infectious diseases by widespread use of
vaccination. For example, Canine Distemper may have accounted for
ten percent of illness in dogs treated by vets in the years
before 1964. Now it is a very rare occurrence in any part of the
U.S., thanks to vaccination. Since Canine Parvovirus first
occured in the late 1970’s the number of cases would
increase dramatically every year, until vaccination decreased the
incidence dramatically by protecting thousands of dogs.
Most responsible dog owners realize that the minimum care they
can provide is to make sure the animal receives adequate
vaccinations. However, the definition of “adequate” has
been questioned recently. The typical combination vaccine used in
dogs has always been recommended to be given as a series in
puppies and then once a year for the remainder of the dog’s
life. Many studies have been initiated in the past few years to
evaluate the duration of immunity created by all of the commonly
used vaccines in dogs and cats. Most researchers are concluding
that most vaccinated animals have adequate protection against
most diseases for longer than twelve months. However, there is
some question as to how to measure the level of protection.
“Challenging” vaccinated animals by exposure to disease
is probably more accurate, but less frequently done, than
measurement of antibody levels. This is probably because
antibodies only represent one part of the immune system. Cellular
immunity, which involves inflammatory cells and a number of
compounds produced in response to infection, plays a large role
also, but is not easily evaluated. Nevertheless, many researchers
are recommending vaccination for most diseases every three years.
The question of duration of immunity has not been adequately
answered at this time. One way to be sure that your dog is
protected would be to continue vaccination every year whether it
is needed or not. This raises more questions regarding the
dangers of overvaccinating. The potential for adverse reactions
would decrease if we could give vaccines less frequently. Most
vaccine reactions are minor, but recently some researchers have
expressed a concern about autoimmune reactions. This is an
abnormal response of the immune system to any stimulus, not just
vaccines. It involves the immune system damaging the body’s
normal tissues, such as the joints, causing immune-mediated
arthritis, or the red blood cells, causing hemolytic anemia.
Perhaps the strongest argument for vaccinating cats less
frequently is the correlation between the administration of
certain feline vaccines, and the development of sarcomas,
cancerous tumors, at the site of vaccination.
Some researchers have recommended blood-testing dogs every year
to determine their level of protection against certain diseases,
and then only vaccinating those that need it. This sounds like a
good idea, in theory, but there are several problems with this
approach. First, it would probably be more expensive to run blood
tests than to vaccinate annually. Secondly, as mentioned earlier,
antibody levels do not accurately tell us whether an animal is
protected against a disease.
Until recently, the standard methods of producing a vaccine
involved using the organism that is responsible for the disease
that the vaccine is meant to prevent. The organism would be
killed with heat or chemicals, or altered to that it no longer
produces disease (a modified live vaccine). When this is injected
into an animal or person, the immune system is tricked into
reacting as it would if the disease-causing organism were
infecting the body. This leaves the individual prepared to fight
off infection when exposed to the real thing. As mentioned in my
recent article on Lyme Vaccines, another way to produce vaccines
uses recombinant technology to manufacture specific proteins that
are part of the virus or bacteria. These individual proteins are
incapable of producing disease but they can stimulate the immune
system to recognize the organism when it causes infection. These
“purified” vaccines hold the strongest potential to
decrease the serious, life-threatening vaccine reactions that are
occasionally seen with whole-cell vaccines.
We will definitely see major changes in the near future in the
area of canine and feline vaccinations. I recommend that you
discuss the situation with a veterinarian you trust.