Vaccination
The
basics explained; addressing common concerns
Vaccines
are one of the greatest medical developments of the modern era. Thanks to vaccines, many formerly common diseases have been
controlled. Fatal and crippling diseases such as polio, whooping cough, measles, rubella (German measles) have been so reduced
in incidence that many people today have never seen a clinical case. Smallpox, once a great killer, has been practically eradicated.
Our dogs also reap the benefits of vaccination science for control of once-common diseases such as distemper, parvo and rabies.
However,
in recent years, questions have arisen regarding the safety, efficacy and advisability of vaccinations for our canine friends.
Most of these concerns are based solely on anecdotal evidence. A vaccine is given, and days, weeks or months later, a health
problem surfaces. As we search for reasons why our dog was so unlucky to develop this problem, we wonder: did the vaccine
cause the health problem? While it is tempting to blame the health problem of our dog on a prior vaccine, this is the logical
fallacy of coincidental correlation. Simply because one event follows another does not mean that the first event caused the
second. It is just as logical to state that putting gas in your car causes car accidents. Medical problems that occur after
immunization are often blamed on the vaccine, but, in most cases, solid evidence is lacking.
Search
the internet and you will find innumerable websites claiming that vaccines are unnecessary, even harmful.
Much
research has been done on vaccination in humans. Despite the many wild claims about alleged dangers to humans from vaccines
(liver cancer, autism, brain damage, etc), the studies do not support these claims. It is likely that the case for vaccine
dangers in dogs has also been overstated.
Let’s
examine some of these concerns about vaccinations for dogs:
“Vaccines
don’t work”
Vaccines
are highly effective. In several studies, vaccination against specific canine diseases is 100% effective in producing immunity.
However, there are always some individuals who will not develop immunity after vaccination. Poor response to a vaccine may
be due to the neutralizing effect of maternal antibodies circulating in very young puppies. It can also be a result of the
vaccine losing its potency when stored improperly. Poor immune response may be due to a weak vaccine challenge (for example,
killed vaccines are not as effective as modified live virus vaccines). Fever and impaired immune response of the host can
reduce vaccine effectiveness. Regardless of the cause, these individuals with poor response to a vaccine have the same risk
of contracting a disease as non-vaccinated dogs. It is due to the variability in response to vaccine that most veterinarians
recommend a puppy “series”, and a second “booster’ vaccination for adults with unknown vaccine history.
In
general, live vaccines are more effective than killed vaccines, and viral vaccines are more effective than bacterial vaccines.
Bacterial vaccines such as kennel cough and leptospirosis, only provide immunity for a few months to a year at most. Luckily,
the core vaccines are modified live viral and, in the case of rabies, killed viral vaccine, with a very high rate of successful,
long-lasting immunity.
Vaccines
are effective in preventing disease not only in individuals, but also in communities. This type of protection is called “herd
immunity.” Herd immunity works by decreasing the numbers of susceptible individuals. When this number drops low enough,
the disease will disappear from the community because there are not enough individuals to carry on the catch-and-infect cycle.
According
to Ron Schultz, PhD, vaccine researcher the University of Wisconsin, although the
US probably vaccinates more dogs than
any other country, our coverage is only about 50% of the total canine population. “With anther 20-25% covered, we could,
for all practical purposes, eliminate these disease, because we would have so much better herd immunity,” Schultz stated
at a 2007 canine health conference.
“Vaccines
are not safe”
In
truth, few things meet the definition of “safe”. For example, every year in the U.S., 350 people are killed in bathroom or shower-related accidents, and 200 are
killed choking on food. Yet few of us regard taking a shower or eating as unsafe activities.
No
vaccine is 100% harmless. Almost all vaccines can cause pain, redness, or tenderness at the site of the injection. In addition, vaccination during the perinatal period can cause abortion, congenital
anomalies, fetal death, and failure to conceive. More rarely, some individuals may develop transient immune
suppression, arthritis, autoimmune hemolytic anemia, encephalitis, and seizures, The distemper vaccine is also under
investigation as a possible cause of hypertrophic osteodystrophy. Vaccines can also cause fever and malaise, and (extremely
rarely) death. It should be noted that these risks also occur with a naturally-acquired infection.
Allergic
responses can result from serum components in the vaccine. A Banfield study done in Florida
in 2001-2002 revealed a rate of severe anaphylactic reaction of 1 dog per 5000 (out of a study done on 838,015 dogs).
We
need to understand that diseases such as distemper, parvovirus and rabies often cause permanent disabilities and fatalities.
The risk of the vaccine must be weighed against the very real risk of contracting the disease.
“Vaccines
are not necessary”
In
some ways, vaccines are victims of their own success. Many dog owners today have never seen a case of distemper or parvo.
As a result, they may question the continued need for vaccines. However, the disease organisms remain in the environment and
a danger to every unvaccinated dog. Herd immunity is also some protection for unvaccinated dogs, but it is by no means a guarantee
that the dog will not succumb to an infectious disease.
Rabies
is transmissible to humans and invariably fatal; consequently, rabies vaccination and re-vaccinations are legal requirements
in all states. Rabies is a killed, adjuvant vaccine with higher risk of adverse reactions. There is an ongoing rabies challenge
study at this time, to determine duration of immunity obtained from rabies vaccination. If results are as expected, this will
hopefully provide a basis for lengthening the legally mandated rabies vaccine administration intervals.
Some
people believe that by not vaccinating, they can develop, through “survival of the fittest”, a strain of dogs
with “natural resistance” to infectious disease. To illustrate the fallacy of this sort of idea, let’s consider
that most deadly of zoonotic contagious diseases, rabies. The existence of this disease has been documented since at least
2300 B.C., and has likely existed for many millennia prior to that. If it were possible to develop a natural resistance to
rabies through non-vaccination and “survival of the fittest”, rabies would have ceased to be a threat centuries
ago, as the less fit, less immune animals died from the disease. Yet we humans and our dogs remain 100% vulnerable to rabies,
and only through recent advances involving immunoglobulin administration and vaccinations have diseases like rabies become
a reduced threat.
While
in the US we have reduced risk of many
infectious canine diseases, canine rabies and adenovirus (infectious hepatitis) have recently been found in imported dogs,
so the continued threat of disease remains very real.
“Puppies
are too young to be vaccinated”
Because
young puppies have had limited exposure to diseases in the environment, they have little developed immunity and are more vulnerable
than adults to contract infectious diseases. They receive protection from their mother’s antibodies for several weeks,
but once that protection wears off, it could be argued that vaccination is more important for young puppies than for mature
dogs.
The
age to begin core vaccination in puppies is a topic of much debate. AAHA 2006 guidelines suggest the earliest age in normal
circumstances should be 6 weeks, but in the face of an outbreak or in a shelter/rescue situation, vaccination can begin at
an even earlier age. Rabies is not recommended to be given until after age 12 weeks. Studies in humans have shown that children
are fully capable of responding to vaccines in the first months of life. Studies in dogs have produced similar results.
“It
is best not to give more than one vaccine at a time.”
Puppies
are capable of responding to millions of different bacteria and viruses because they have billions of immunologic cells circulating
in their bodies. Therefore the vaccines given in the first few month of life are literally a raindrop in the ocean of what
the puppies’ immune systems successfully encounter in their environment every day.
Studies
on human infants show that multiple combined vaccines are easily handled by the immune system.
A
Banfield study on dogs indicates that the risk of overall reactions is slightly increased with multivalent vaccines (27 per
10,000) as opposed to single vaccines (7 per 10,000). However, most reactions were transitory and not clinically significant.
Also, since the dogs received multiple different antigens simultaneously, a reciprocal increase in reaction rate could reasonably
be expected. There was an overall reaction rate of 16 per 10,000 dogs in this study; with 2 per 10,000 dogs vaccinated suffering
serious anaphylactic reactions.
“Vaccines
cause dogs to develop autoimmune disease”
Results
from studies on families and twins show an important role in both genetic and environmental factors in the eventual development
of autoimmune disease.
The
portion of the genome that codes the genes that help us recognize “self” is called the MHC-the Major Histocompatibility
Complex. These genes are located very close to each other and it is rare for recombination to occur. This in effect means
that the genes from each parent are inherited intact. (Remember, you inherit genes in pairs, one from each parent). If the
parents are closely related, the possibility exists that they share the same genes at that site…they are “homozygous
by descent”. If so, there is a high likelihood that their offspring will inherit identical genes in the MHC. It
appears that susceptibility to an autoimmune disease is determined by the lack of variability in the MHC genes. Linebreeding
and inbreeding may result in this lack of variability. Close breedings increase susceptibility in the offspring to
develop an autoimmune disease when an environmental trigger is present.
Though
the tendency to autoimmunity is genetic, most autoimmune diseases are triggered by some sort of toxic assault, or viral or
bacterial exposure. Scientist believe that the body reacts to small protein-like fragments of the vaccine base that
are similar in structure to the normal cellular components of the body. A recent study showed that vaccine contaminants may
cause the dog to make antibodies against these contaminants. Not all the vaccinated dogs in this study developed this response….and
those who did were in the same particular family group, further reinforcing the genetic basis of autoimmunity.
Dogs
who are genetically susceptible to the autoimmune process are at greater risk for such problems as thyroiditis, hypertrophic
ostedystrophy, and autoimmune hemolytic anemia. These conditions may be provoked by vaccination and/or infection. However,
as noted by Dr. Schultz, vaccines may trigger autoimmune disease, but they do not cause it. And, if dogs do not receive their
core vaccines, Dr. Schultz notes, “They won’t go on to develop thyroiditis. They’ll die from distemper or
parvo.”
Naked
DNA vaccines are under development. These vaccines would contain solely the desired antigen, with no bovine contaminants.
This would mean that when this type of vaccine is given, antibodies specific for the disease would be produced, without the
high risk of allergic reactions or antibody responses to bovine components.
“My
dog is too small to be vaccinated”
Small
breeds, and several specific breeds, are at higher risk of adverse vaccine reactions. A Purdue study involving more that a
million dogs found that dogs 22 lbs or less had approximately twice the risk compared to dogs weighing over 22 lbs. The one
milliliter dose volume listed on most vaccine labels is recommended only because that is the dose used for the licensing process.
During testing, the issue of breed or size of dog has received no attention. Since we have research indicating a higher risk
of reaction to vaccines by small dogs, hopefully some studies will be done to determine the lowest effective dose for toy
breeds and breeds at higher risk of reaction such as Chihuahuas,
miniature pinschers, Boston Terriers and dachshunds. According to Dr. Schultz, body size is less critical with biologics than
pharmaceuticals, and a toy poodle is as likely to need a full dose of a vaccine as a Saint Bernard.
Vaccine
Basics
The
goal of a vaccination program is to develop immunity to serious diseases while minimizing risks of allergy and inappropriate
immune response.
Natural
infection and recovery from a disease confers long-lasting immunity. A vaccine can also have the same beneficial effect on
immunity.
The
oldest and most common vaccine is the MLV (or modified live virus) vaccine. The actual disease-causing viral organism (the
“antigen”) is cultured, then altered so that it won’t cause disease symptoms. Another type of live vaccine,
the vector vaccine (VV), is a genetically engineered vaccine which is also very reliable and safe. Both MLV and VV are infectious
vaccines. They work by producing a mild disease response in the individual. When the VV or MLV vaccine is given, the body’s
immune system responds by producing antibodies which kill the virus. Immunologic memory allows the immune system to remember
the organism to which it has been previously been exposed. Duration of immunity is determined by the memory cells, but the
only way these cells respond is if the individual becomes infected. Due to the live virus which is introduced to the memory
cells through use of a live vaccine, the VV/MLV vaccines induce reliable and long-lasting immunity. A stressed, ill, or immunocompromised
dog should not receive a live vaccine.
Another
type of vaccine is the noninfectious vaccine, “killed” or “subunit” vaccine. The virus or bacteria
is actually killed by use of radiation or a chemical, and cannot produce disease. This type of vaccine has less chance of
producing disease symptoms, but may also be less effective in provoking immunity in the host. Rabies vaccine is killed, so
that there is no chance of the dog developing a fatal case of rabies. Manufacturers may add “adjuvants” or immune-boosting
substances, to the killed vaccines in an attempt to improve their effectiveness. These adjuvants often produce adverse side
effect such as local inflammation, allergy, and (in the case of one in ten thousand cats) tumor formation at the vaccine site.
Cats lack the tumor suppression gene that would act on an injection site that is inflamed by certain vaccine adjuvants, particularly
from rabies and feline leukemia vaccine. This problem in cats has prompted researchers to attempt to develop safer, purer vaccines.
“Core”
vaccines recommended for dogs are distemper, adenovirus (hepatitis), parvovirus and rabies. These are all viral vaccines which
readily provoke cellular memory and induce long-term immunity. There should be a dose of core vaccine at 14-16 weeks as the
final dose in the puppy series, then at age one year, then after that not more than every three years,with the exception of
rabies. Rabies should be given once some time after age 12 week, and then not more often than required by local law. Minimum
duration of immunity from the core vaccines is thought to be seven to ten years. Yearly vaccination is outmoded and unnecessary,
and exposes the dog to an increased risk of an adverse reaction. Those reactions are rare, but unacceptable if your dog receives
something he doesn’t need and consequently dies.
Blood
levels of antibodies can be measured. This is known as a “titer test”. There is no standardization between different
labs and their testing methods, and testing can be costly. The presence of antibodies may indicate a level of protection against
a certain disease; however, titer levels needed to infer protection from disease are not known. Titers can be positive
in puppies as a "gift" from the mother, and do not necessarily indicate active immunity in the puppy. Titers can
be elevated in dogs incubating a disease, who are actively contagious! Therefore, it is not possible to know if a given
titer in a specific animal indicates adequate immunity. In the future, measurements of titers may provide a method of
determining intervals for re-vaccination.
Vaccine
programs should be individualized depending on the age of the dog, the breed, and the diseases prevalent in the area. Consult
the American Animal Hospital Association Canine Vaccine Guidelines (2006) for the most recent recommendations:
http://www.aahanet.org/PublicDocuments/VaccineGuidelines06Revised.pdf
"Vaccination
Dos and Don'ts"
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1. Do Not
Vaccinate Needlessly
Don’t revaccinate more often than is needed and only with the vaccines that prevent diseases
for which that animal is at risk.
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2. Do Not
Mix Vaccines in a Single Syringe
If the vaccines are not combined by the company as a multicomponent licensed product, do not combine
them prior to administration. Follow the manufacturer’s administration recommendations.
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3. Do Not
Split Doses
For miniature/toy or any other breeds. If you are concerned about the volume, reconstitute vaccine
with
1⁄4 or 1⁄2 the recommended diluent (e.g., sterile water).
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4. Do Not
Vaccinate Anesthetized Patients
Should an anesthetized animal develop a hypersensitivity reaction, they may vomit and are at increased
risk of aspirating.
1
5. Do Not
Vaccinate Pregnant Dogs
The dog may abort or fetuses may get infected.
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6. Do Not
Vaccinate Animals on Immunosuppressive Therapy
These animals may not develop an adequate immune response, but even worse, they could develop disease (e.g., postvaccinal distemper, clinical canine parvovirus).
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7. Do Not
Administer Multiple Dose Vaccines Any More Frequently Than Every 2 Weeks
1
8. Do Not
Vaccinate Puppies <2 Weeks of Age
1
9. Do Make
Sure the Last Dose of a Puppy Immunization Series is Administered ≥12 Weeks of Age
At
≥12
weeks of age, interference by maternal antibody is less of a concern and the puppy’s immune system is more
mature; thus, there is a greater opportunity for a robust immune response to the vaccine.
10.
Do Not Give an Inactivated Product Prior
to a Modified Live Product
This will interfere with the ability of the modified live product to immunize (e.g., canine parvovirus-2).
11.
Do Not Administer a Canine Distemper-Measles
Vaccine Subcutaneously (SC)
It has been shown that poor immunity results when this product is administered SC.
12.
Do Not Assume that Vaccines Cannot Harm
a Patient
Vaccines are potent medically active agents and have the very real potential of producing adverse
events.
13.
Do Not Use Nosodes (Holistic Vaccines)
to Vaccinate a Puppy
Nosodes do not provide immunity; thus, the puppy will remain susceptible to the disease the nosode
was designed to prevent. Use a USDA-licensed vaccine to immunize puppies.
14.
Do Not Revaccinate a Dog With Vaccines
Previously Known to Induce Anaphylaxis in that Dog
Test the animal’s serum for antibody to determine if the animal is immune. The risk from
vaccine-induced anaphylaxis may be much greater than the risk of infection
15. NEVER vaccinate an animal who is ill or debilitated.
References
Novak,
Will, DVM, MBA; “Predicting the ‘Unpredictable’ Vaccine Reactions”; Proceeding of the NAVC Congress,
2007.
Schultz,
Ron, PhD; “What Everyone Needs to Know About Canine Vaccines and Vaccination Programs”; AKC CHF Health conference,
St. Louis, MO, Oct 2007.
Fortney,
William, DVM “Newest Vaccination Strategies for Sporting Dogs”, North American Veterinary Conference, 2006.
Thorpe-Vargas,
Susan, PhD. “Genetic and Breeding Strategies: Essays for the Dog Breeder”.
Offitt,
Paul A., M.D.and Bell, Louis M, M.D., “Vaccines; What
You Should Know”; 3rd edition, 2003..
Hogenesch,
Harm, Azcona-Olivera, Juan, Scott-Moncrieff, Catharine, Snyder, Paul W.,and Glickman, Larry T., “Vaccine-Induced Autoimmunity
in the Dog”; Advances in Veterinary Medicine, Vol 41, pp 733-747.
Rynders,
Patricia E., DVM, MS; “New
Protocols for Canine Vaccination”; Canine Pediatric Care Symposium,WSAVA 2005.
Greene,
Craig E., “Avoiding Vaccine Reactions in Dogs and Cats”; WSAVA 2003.
Roth,
J. A., DVM, PhD; “Factors Influencing Vaccine Duration of Immunity”; The North American Veterinary Conference;
Jan, 2007.
Maybury,
Bonnie A. and Peters, Pamela M., PhD; “Vaccines—How and Why?”; http://www.accessexcellence.org/AE/AEC/CC/vaccines_how_why.php
