Re-Vaccination: Vaccination for Previously Vaccinated Dogs and Older Puppies
By Christie Keith

This article is meant to inform you of research, opinions, and personal reflections that might be useful to you in determining a disease prevention program for your pet. It is educational in nature, and is not intended as veterinary advice. The author cannot be held responsible for any unfavorable results from the use of this information. Readers should seek professional veterinary advice for any health decisions involving their pets.

Annual shots: Many veterinarians insist on them, boarding kennels and groomers require them, and keeping “current” on vaccinations has become one of the hallmarks of responsible pet ownership. But are they really necessary? And are they safe?

In recent years, these questions have risen to the forefront of veterinary medicine, and it’s more common than it used to be for pet owners as well as veterinarians to be struggling with them. I also wish I could tell you that there is a concensus about the answers to these questions, based on science and research; there isn’t. All I can tell you is that ultimately, no matter what your veterinarian suggests, or what I believe, or what you read as you research this issue, this is your decision to make.

Are Vaccines Really Harmful?
Some have attributed every ill of the canine and feline pet populations, from allergies to arthritis to severe immune system breakdowns, to excessive use of vaccines. Others, most notably vaccine manufacturers, insist the vaccines are harmless and that the benefits outweigh the risks. Where does the truth lie?

A few years ago, the Colorado State University School of Veterinary Medicine became the first veterinary college to issue a vaccination schedule that recommended against annual vaccinations. In their new protocol they wrote, “We are making this change after years of concern about the lack of scientific evidence to support the current practice of annual vaccination and the increasing documentation that over vaccinating has been associated with harmful side effects. Of particular note in this regard has been the association of autoimmune hemolytic anemia with vaccination in dogs and vaccine-associated sarcomas in cats…both of which are often fatal.”

There is some evidence to suggest to even the most ardent vaccine supporter that there are risks to vaccination. In cats, there is an alarming incidence of injection site sarcomas, an aggressive and often fatal cancer. In dogs, there is a correlation between autoimmune hemolytic anemia and vaccination (Dodds, 1985; Duval and Giger, 1996), and an ongoing study at Purdue University has found that vaccinated dogs, but not unvaccinated controls, have formed antibodies to their own cells (Larry T. Glickman, DVM, “Weighing the Risks and Benefits of Vaccination,” Advances in Veterinary Medicine, Vol. 41, 2001). Immunocompromised dogs vaccinated for canine distemper have been reported to develop post-vaccinal encephalitis (Meyer, “Vaccine Associated Adverse Events,” Veterinary Clinics of North America, May 2001). Dogs with inhalant allergies are known to worsen after vaccination (Frick and Brooks, 1983).

According to leading canine vaccine researcher Dr. Ronald Schultz, Chair of the Department of Pathobiology at the University of Wisconsin-Madison School of Veterinary Medicine, and editor of the textbook Veterinary Vaccines and Diagnostics, “It is becoming increasingly more evident that it is no longer true to say, ‘Well, even if the vaccine doesn’t help, it won’t hurt.’ There are some canine vaccination programs that have no scientific justification that may have the potential of causing harm.”

So What Do You Do?
I know we’d all like to think we can put a magic barrier around our animals that will protect them from all disease and have 100 percent effectiveness and no risk. The closest you’ll ever get to that is to build a barrier of radiant good health, which comes from excellent breeding practices, never suppressing disease symptoms, and excellent holistic husbandry including diet, environment, exercise, and TLC.

In the real world, such a barrier will never be perfect. We have to accept some risk in one direction or another.

Those who don’t vaccinate at all must accept the risk that the animals in our care might get sick from an infectious disease; with puppies, the risk is great that they will die, and even if they live, they might have lingering effects from the disease, and the vet bills (and feelings of guilt) might be considerable. Those who do vaccinate must accept the risks of side effects, allergic reactions, vaccine failures, cancer, and autoimmune disease.

Everyone has to educate themselves the best they can, weigh the risks vs. benefits, and come to their own decision. If what you want is zero risk and all benefit, it doesn’t exist and you will never find it.

Am I saying vaccines are harmless? No. I think they do a lot of harm. I manage to believe that while still knowing and acknowledging that they are also effective in protecting against certain acute diseases. They are in fact so effective that most people reading this, whose dogs have already been immunized against parvo and distemper, really are on very solid ground when they stop vaccinating, because their dogs are already immune.

For those people, the decision not to vaccinate at all is not on the table. The animals have already been vaccinated. The only question is, do you need, or want, to give them “booster” shots? If not, how can you be sure your animal is fully protected against disease? If yes, what boosters should be given, and how often?

There are some general guidelines and immunology studies that might be useful to you in researching whether or how to give booster shots to your dogs. First, I want to stress that all of this information is based on an assumption that your dog was successfully vaccinated in the past. That is a big assumption to make, and before making it, please be sure you have read my section on puppy vaccination. Just because your dog had vaccines given in the past does not guarantee that those vaccinations were successful and that your dog is in fact immune to those diseases.

What Vaccines are We Talking About?
Let’s look at the commonly used canine vaccines.

Other than rabies, the two most serious canine viral diseases are canine parvovirus and canine distemper. (Since rabies vaccination is a matter of law, rather than science, I’m not going to discuss it here.) According to Dr. Schultz, protection against canine parvovirus and canine distemper from successful vaccination is long term, probably lifelong. (Kirk’s Current Veterinary Therapy XIII; 2000; “Vaccines and Vaccinations: Issue for the 21st Century”, Richard B. Ford and Ronald D. Schultz; (Kirk’s Current Veterinary Therapy XI, “Canine and Feline Vaccines,” Phipps, Schultz; R.D. Schultz, “Considerations in Designing Effective and Safe Vaccination Programs for Dogs,” May 2000; (Schultz, “Duration of Immunity to Canine Vaccines: What We Know and Don’t Know.”)

What About the Other Vaccines?
The other common canine vaccines are Canine Adenovirus-2 (CAV-2), also known as Canine Infectious Hepatitis; Canine Bordatella (a bacteria that is part of the kennel cough complex); Canine Parainfluenza (a virus that is part of the kennel cough complex), Leptospirosis (a bacteria that causes kidney disease), and Canine Coronavirus, an intestinal virus. Other canine vaccines that are sometimes given are for Lyme disease and Giardia.

Canine Infectious Hepatitis (CAV-2)
There has been no case of infectious hepatitis in the US in 20 years, according to Dr. Schultz. This vaccine does cross-protect against CAV-1, part of the kennel cough complex (see below).

Kennel Cough
The kennel cough complex (bordatella, parainfluenza, CAV-1) is a set of treatable diseases similar to a cold. A normal, healthy animal shouldn’t become seriously ill with any of them. Immunity to CAV-2 (infectious hepatitis) gives cross protection to CAV-1, and the CAV-2 vaccine provides a similar duration of immunity to parvo and distemper (many years, probably lifelong). The bordatella vaccine is not long-lasting, since both natural and vaccine bacterial immunity are always temporary, and I believe, considering how often you have to repeat it, the risk mounts up until it outweighs the benefit. Parainfluenza vaccine (a virus) is considered to be extremely effective, however, again, I consider the risk to outweigh the benefit for the whole kennel cough complex. I have never given any of these vaccines in the period since November 1985 and have never had a dog get any of them, despite being at shows, classes, dog parks, and living with someone who worked in shelters and had foster dogs at our house who had active kennel cough.

Some dogs do develop pneumonia or other complications from kennel cough. I consider this to be rare, and also a sign that the dog had a pre-existing susceptibility to respiratory problems. However, it’s important to realize that the risk, even if rare, does exist, when deciding on a course to follow as regards kennel cough vaccination.

This vaccine has more adverse effects reported than all other canine vaccines combined. It’s not very effective and even when it does give protection, it doesn’t last very long. Most dangerously, while it prevents expression of disease in dogs, it does not prevent them from shedding the bacteria. This carrier state makes them a risk to other animals and people, because they can “have” lepto and you don’t know it. (Lepto is transmissible to humans.) Again, to me, the risk outweighs the benefit.

Lepto is treatable if caught early. In most cases, the reason lepto is so dangerous is that owners and veterinarians don’t think of it fast enough. Learn the symptoms of leptospirosis and if your dog shows any of them, don’t delay; have him or her tested and treated for lepto immediately. As with kennel cough, a few dogs do become very ill, or even die, from leptospirosis, despite treatment. I have an article specifically on the risks and benefits of lepto vaccination here.

Giardia is an opportunistic pathogen. If a dog is healthy, giardia will naturally be kept in check by beneficial microbes and the dog’s immune system. Very large numbers of dogs in California who are totally asymptomatic can have giardia cultured from their stool. I am not aware of any veterinary schools, or immunology or vaccine researchers, who recommend the use of this vaccine.

This is the classic “vaccine in search of a disease.” Except in very young puppies, coronavirus does not seem to cause clinical disease in dogs. They cannot induce disease with it in the laboratory. Many, perhaps most, dogs have coronavirus in their intestine all their lives. (Schultz, “Emerging Issues: Vaccination Strategies for Canine Viral Enteritis,” 1995.) According to Texas A&M University’s “Vaccine Protocols and Schedule,” “(T)here are no studies that show that use of the vaccine reduces morbidity or mortality. (Mansfield 1996.) The risk has to be said to outweigh the benefit on this one, as there doesn’t appear to be any benefit.

Lyme Disease
Lyme Disease is caused by an organism called Borrelia burgdorfieri, which is transmitted by a tick. Borrelia is a spirochete, a highly coiled bacterium.

Lyme Disease is very serious in humans, although scientific opinion generally holds that it is rarely serious in dogs. Most experts contend that it causes only brief acute illness in dogs, or no symptoms at all. Dogs in endemic areas will often test positive for Lyme and have no symptoms, or at least, no observable symptoms.

Many dog owners, and some veterinarians, don’t agree with this view, and claim to have observed serious debilitating disease in their dogs as a result of infection with Borrelia.

There is also debate over how widespread Lyme disease really is. Some argue that since 90 percent of human Lyme cases occur in 100 counties in eight states, it’s not widespread at all. Others point out that Lyme is grossly underreported and underdiagnosed, and epidemiology information on this disease is probably a few years behind, as well.

I don’t know the truth of the situation. There are many tick borne diseases that we know, but more that we don’t. Most ticks do have more than one of these, and if a dog has contracted Lyme, they probably also contracted one of the others. Perhaps both groups are correct, and one of the other tick diseases is actually responsible for the sick dogs’ symptoms. Or perhaps current conventional thought is wrong, and Lyme really is serious and common in dogs.

Despite these controversies and despite the potential seriousness of the disease, the following points convince me that this vaccine is not a good one, even in endemic areas:

One, 19 of 27 veterinary colleges in North America do not give Lyme vaccination, and the other 8 only give it if the owner requests it.

Two, it can often cause inflammatory arthritis in dogs who get it, just like Borrelia itself can. However, unlike natural Borrelia infection, antibiotics have no effect on the vaccine-induced form of the disease.

Three, the human version of this vaccine was removed from the market.

Four, like all bacterial vaccines, immunity doesn’t last long and thus the vaccine needs frequent repetition to be effective, which means you are exposing your dog to the risk again and again, unlike viral vaccines which provide years, probably a lifetime, of immunity.

Five, I question how useful this vaccine is:

“One study in an endemic region demonstrated that 89.6 percent of healthy dogs had positive Lyme titers. There is no apparent correlation between positive Lyme titers and the occurrence of clinical signs. Only 4.8 percent of naturally exposed seropositive dogs demonstrated a limb or joint disorder with lethargy, fever, or inappetence; however, 4.6 percent of seronegative dogs also demonstrated such disorders. Most dogs that are seropositive for Lyme disease have not exhibited clinical signs of the disease.” (Why I Don’t Use Lyme Disease Vaccines, Meryl P. Littman, VMD, ACVIM; Department of Clinical Studies School of Veterinary Medicine, University of Pennsylvania; Compendium on Continuing Education for the Practicing Veterinarian, November 1997.)

[UPDATE: A more recent study found that nearly all dogs deliberately infected with Lyme did show symptoms. However, while this changes the concept of whether or not to TREAT asymptomatic Lyme infection, it does not change my view on whether or not the vaccine is a good one. It’s not.] Read more about Lyme disease in dogs here.

How Long Does Vaccine Immunity Last?
The only correct answer to this is that no one really knows. Duration of immunity tests are done by vaccine companies, but usually run only for one year, although there are, as of 1995, two approved and one pending canine combination vaccines with three-year duration of immunity tests. It’s not that the vaccination “wears off” after a year or three years, but that the test ended at one year or three years.

The difference between the one-year and three-year vaccines is they ran a longer duration of immunity test to be able to make a label claim of three years. It’s a marketing strategy, period. Any seroconversion that takes place after a modified live virus vaccine for parvo, distemper, parainfluenza, or adenovirus-2 (the “DHPP” of the combo shot) is just as good and as lasting as any other seroconversion, whether obtained from a vaccine with a one-year label claim or a three-year label claim.

Since epidemiology tells us that canine parvovirus and canine distemper are almost unheard of in vaccinated adults, we can conclude that in most cases, the immunity from those vaccines lasts many years, probably a lifetime. What about the others?

Vaccines for bacterial disease do not usually provide long-term immunity. This is true of natural infection, also. It’s why you never get chicken pox (a virus) again after you’ve had it once, but you could have strep throat (a bacteria) many times during your life. Bacterial vaccines for dogs are bordetella, leptospirosis, and Lyme disease. If you have decided to use these vaccines, you need to be aware that the immunity they provide will not last, and you will need to repeat the vaccinations at certain intervals. What those intervals are will depend on your own unique circumstances. Obviously, this need to give the vaccine repeatedly increases the risk of the vaccination.

Specific duration of immunity information for these and other canine vaccines is available in Dr. Schultz’s article “Considerations in Designing Effective and Safe Vaccination Programs for Dogs.”

No “Booster” Effect
Since no one can be absolutely sure that an animal is immune to something unless they actually encounter it, some people feel that it’s best to give “booster shots” to increase immunity. Some breeders like to give “booster shots” to their bitches before breeding them, so they’ll have plenty of immunity to pass on to their puppies. Other owners just feel safer giving “booster shots,” and of course, most veterinarians truly believe that they should be given “just in case,” on a schedule that will commonly range from every year to every three years.

The only flaw in this reasoning is that it doesn’t appear that giving shots to already-immune animals “boosts” much of anything. You cannot make an immune animal “more immune.” Re-vaccinating an already-immune animal has little or no benefit; the previous immunity will act like maternal antibody and inactivate the vaccine, and immunity is not “boosted” at all. So you have all the risks of the vaccination, and no benefit. (Schultz, R.D., “Current and Future Canine and Feline Vaccination Programs.” Vet Med 3: No. 3, 233-254, 1998.)

What Can I Give My Dog to Minimize the Negative Effects of Vaccines?
The same thing that protects your dog from disease is what will protect them from the ill effects of vaccination: Radiant good health. There are no shortcuts to good health. It involves breeding and feeding for health, as well as giving clean air, clean water, plenty of appropriate companionship, mental stimulation, and exercise. Most of us have dogs whose genetics are not in our control, and in many cases, neither were their early lives. Those animals are probably not healthy enough to resist disease on their own, but sadly, they are the very dogs who are most likely to be negatively affected by vaccination.

Many people routinely use and recommend the homeopathic remedy thuja to counteract vaccine effects. Thuja’s reputation for helping with vaccine reactions arose during the days when the only vaccine that existed was the smallpox (cowpox) vaccine. The blanket use of thuja to protect after a vaccination is not based on homeopathic principles, and using thuja in this way is at best pointless (unless it happens to be the right remedy to match your dog’s unique symptoms). What you need to do, if you decide to vaccinate and want to address side effects with homeopathy, is observe the dog for his or her own unique reaction and symptom picture, and pick the single most similar remedy. In other words, the remedy which, when given to healthy people, produces the same symptom picture which your ill dog has. This is not something a pet owner should do on their own, but only with the advice of a skilled homeopathic veterinarian.

Make sure that your animal is extremely healthy when they are given vaccines. Not only are vaccines licensed for use in healthy, clinically normal animals only, an animal who is sick will probably not be able to form good immunity in response to the vaccination. They will suffer increased risk and reduced benefit.

Many people like to give herbal supplements before and after vaccination. Gentle herbs such as Echinacea, Oregon grape, and others might well have some benefit to your dog. For more information on using herbs or supplements to combat the negative effects of vaccination, consult a holistic veterinarian or the book Herbs for Pets by herbalists Mary Wulff-Tilford and Greg Tilford.


Note: In the references below, I cite two editions of Kirk’s Current Veterinary Therapy, the 11th, published in 1995, and the 13th, published in 2000. The 14th Edition was published in May of 2005, and is available here. Kirk’s is the single most clicked-on book title on my site, but is rarely purchased as it costs around a hundred dollars. It is, however, a very valuable reference book and I highly recommend it.

1. “The incidence of canine distemper, canine parvovirus, canine adenovirus, and feline panleukopenia among vaccinated adults (>1 year of age) is virtually zero. The correlation among vaccination, the development of a “positive” antibody response, and protection from exposure to virulent virus is excellent. Furthermore, protection from exposure derived from immunization is sustained for periods as long as 5 or 6 years or more.” (Kirk’s Current Veterinary Therapy XIII; 2000; “Vaccines and Vaccinations: Issue for the 21st Century”, Richard B. Ford and Ronald D. Schultz.)

2. “A practice that was started many years ago and that lacks scientific validity or verification is annual revaccinations. Almost without exception there is no immunologic requirement for annual revaccination. Immunity to viruses persists for years or for the life of the animal.” (Kirk’s Current Veterinary Therapy XI, “Canine and Feline Vaccines,” Phipps, Schultz.)

3. “In our studies, puppies vaccinated annually with modified live CPV-2, CDV and CAV vaccines received no added benefit from annual revaccination throughout a period of 7 years when compared to dogs that were vaccinated as puppies then challenged with virulent virus at 7 years of age. Both groups of dogs were protected from challenge infection with CPV-2, CDV and/or CAV.” (R.D. Schultz, “Considerations in Designing Effective and Safe Vaccination Programs for Dogs,” May 2000.)

“(W)e have found that annual revaccination, with the vaccines that provide long term immunity, provides no demonstrable benefit and may increase the risk for adverse reactions.” (Schultz, “Duration of Immunity to Canine Vaccines: What We Know and Don’t Know.”)

4. “Companion animal vaccination guidelines are currently undergoing critical scrutiny by representatives from private practice, industry, and academia. Despite widespread recommendations for annual revaccination, information available today suggests that current vaccination practices in North America do not necessarily correspond with the body of knowledge pertaining to duration of immunity from licensed vaccines. As a direct result, companion animal practitioners should expect significant changes in the current standard of practice pertaining to the administration of vaccines to dogs and cats.

“Among the most significant changes anticipated in the future will be the recommendation to discontinue routine administration of annual booster vaccinations to adult dogs (distemper virus and parvovirus) and cats (panleukopenia, feline herpesvirus 1, and feline calicivirus). The incidence of canine distemper, canine parvovirus, canine adenovirus, and feline panleukopenia among vaccinated adults (>1 year of age) is virtually zero. The correlation among vaccination, the development of a “positive” antibody response, and protection from exposure to virulent virus is excellent. Furthermore, protection from exposure derived from immunization is sustained for periods as long as 5 or 6 years or more. (Kirk’s Current Veterinary Therapy XIII, published in 2000:”Vaccines and Vaccinations: Issue for the 21st Century”, Richard B. Ford and Ronald D. Schultz.)

5. These notes were taken by Betty Lewis, AHT, from a seminar she attended given by Dr. Schultz in August 2001, and are used with permission:

Core Vaccines are distemper, adenovirus, parvo and rabies. He says all dogs must have these.

His protocol is to give a single vaccine (he recommends the 5-way with the lepto left out) at 12-14 weeks of age. Wait two weeks and run parvo and distemper titers. If the dog has an adequate titer measure at Cornell as 1:100 or higher, there is no need to repeat either the vaccination or the titer for the life of the dog. Rabies is given separately and has to be re-vaccinated by state law.

**Giving multiple vaccinations does not boost immunity, and, in some cases may erode it.

Even though he recommends that the titer level be 1:100, he does not recommend re-vaccination unless there’s a really low titer. He says it probably won’t improve immunity, though it may make you feel better.

Principles of basic vaccine protocol include having breeders give vaccinations at home so puppies don’t go to the vet’s office (sources of infection).

The rabies vaccine is the most reacto-genic, he said, so best to give it separately. Benadryl can be given prior to a rabies vaccine. It will “dampen” the reactive effect of the adjuvants, but won’t interfere with the immune response.

Giardia vaccine is not recommended and a side effect is granulomas at the site.

Immunologic imprinting
This refers to the fact that the immune system should be vaccinated only when it is ready and at its optimum. If you vaccinate an immature immune system or one not capable of responding fully for any reason, and you get only a partial response, re-vaccinating will never give a better response.

There has not been a recorded case of canine infectious hepatitis in the US in the last 20 years. (CAV-2)

“Of course vaccines can trigger neurological and endocrine diseases; didn’t I say that there is an intimate relationship between the immune, neurological and endocrine systems?”

By law the vaccine companies have to put 2-3 times the required dose into the vial.

If a breeding dog can’t develop a titer, it’s not a good breeding prospect b/c it will pass on the poor immune system.

The three species with the most tendency to auto-immunity are humans, dogs and inbred mice.

He said that boosting a mother’s vaccine prior to pregnancy will not increase the level of maternal immunity in the puppies. It is safer for the bitch to wait until after weaning to vaccinate.

6. “In the past, it was believed that annual vaccination would not hurt and would probably help most animals. However concerns about side effects have begun to change this attitude. One disadvantage to over-vaccinating is cost. The client is paying for something with no effect or with the potential for an adverse reaction. I believe that adverse effects are increasing because we are putting more and more components into these animals …There is a real concern that vaccines may predispose certain genetically susceptible individuals to immune-mediated disease. The more antigens we administer, the higher the potential for hypersensitivity. Type 1 is IgE mediated; type 2 cytotoxic antibody mediated; type 3 immune-mediated, type 4 cellular mediated. All of these hypersensitivies are natural parts of the immune response, but they cause a certain amount of tissue damage. In many cases it is impossible to show a direct connection between damage and a vaccine, since it is the accumulation of many antigens over many years that results in clinically evident disease.” (From The Journal of the American Veterinary Medical Association, vol. 207 Aug 15, 1995.)

7. “A practice that was started many years ago and that lacks scientific validity or verification is annual revaccinations. Almost without exception there is no immunologic requirement for annual revaccination. Immunity to viruses persists for years or for the life of the animal.” (Kirk’s Current Veterinary Therapy XI, “Canine and Feline Vaccines,” Phipps, Schultz.)

8. “Dogs’ & cats’ immune systems mature fully at 6 months. If a modified live virus (MLV) vaccine is given after 6 months of age, it produces an immunity which is good for the life of the pet (i.e. canine distemper, parvo, feline distemper). If another MLV vaccine is given a year later, the antibodies from the first vaccine neutralize the antigens of second vaccine, and there is little or no effect. The titer (level of immunity) is not ‘boosted’ nor are more memory cells induced. -Schultz, R.D. – Current & Future Canine & Feline Vaccination Programs. Vet Med 3: No. 3, 233-254, 1998.” (Summary from Bob Rogers DVM,

9. “Since the mid 1970’s we have done a variety of studies with various canine vaccines to demonstrate their duration of immunity. From our studies it is apparent, at least to me, that the duration of immunity for the four most important canine vaccines (core vaccines) is considerably longer than one year. Furthermore, we have found that annual revaccination, with the vaccines that provide long term immunity, provides no demonstrable benefit and may increase the risk for adverse reactions.” (Ronald D. Schultz, Professor and Chair, Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, “Duration of Immunity to Canine Vaccines: What We Know and Don’t Know.”)

Web Resources
Considerations in Designing Effective and Safe Vaccination Programs for Dogs
Duration of Immunity
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