Vaccination Decisions

     by Susan Wynn, DVM

Background

Veterinarians claim that annual vaccinations have decimated the incidence of formerly common viral diseases such as feline panleukopenia, rhinotracheitis, feline leukemia, canine distemper, hepatitis, and canine parvovirus. While this is undoubtedly true, many pet owners and some veterinarians have begun to question both the need for annual, life-long revaccination, as well as the long term consequences of vaccination in general.

The Aftermath of a Success Story

Although Dr Jean Dodds suggested, as early as 1983, that autoimmune disease was occurring in certain susceptible individuals as a result of over-vaccination, concurring literature began to appear only in 1992. Phillips and Schultz, of the Scripps Research Institute and University of Wisconsin, respectively, reviewed the state of canine and feline vaccine technology in Current Veterinary Therapy XI. One conclusion was that annual vaccination was a widespread practice with no scientific basis or verification. The immune response to most viruses lasts years.

Dr Schultz further speculated that for most dogs, revaccination is probably only necessary every three years, although the persistence of immune competence may vary, since modified live virus vaccines stimulate a stronger response from the animal than do killed vaccines. Dr Jim Richards, of the Cornell Feline Health Center, has written that duration of immunity in cats is also not well understood, despite the fact that the need for annual revaccination is questionable.

In 1995, an article appeared in the Journal of the American Veterinary Medical Association entitled "Are We Vaccinating Too Much?" The veterinarians interviewed included Dr Schultz, Dr Dennis Macy of Colorado State University, Dr Leland Carmichael, and Dr Fred Scott of Cornell University. These leading veterinary immunologists admit puzzlement at the current situation but stop short of making recommendations, since no studies have been done to show maximum duration of immunity. When asked directly what should be done, Dr Macy recommends continuing to follow vaccine label instructions, but to pressure the USDA to determine the optimal vaccination schedule. The other experts interviewed did not make specific recommendations but emphasized the need for veterinarians to rationally analyze the individual situation and vaccinate accordingly. In general, they felt that cats should be immunized every three years for both FVRCP and rabies, not annually.

Papers and textbooks over the last 15 years indicate that annual revaccination for some diseases was probably not necessary (see Appel 1972), (Green 1990), (Olson 1997), and (Carmichael 1981). After over 15 years of questions about our vaccine practices, things are changing. Veterinarians acknowledge that yearly vaccines have indeed worked to nearly eliminate some illnesses, but now ask, "do we have to vaccinate yearly to get the same results?"

In 1998, the American Association of Feline Practitioners published an official report compiled by an expert panel recommending that yearly re-vaccination be reconsidered. For viral diseases that induce long lasting immunity, it's recommended that vaccines be done only every three years in cats. The American College of Veterinary Internal Medicine and the American Animal Hospital Assocation endorsed the recommendation, and some veterinary schools began recommending three-year vaccine intervals for both dogs and cats (excepting those vaccines that are known to have short durations of immunity, such as feline leukemia vaccine, leptospirosis, kennel cough).

Aside from the question of whether yearly revaccination is necessary, there is the possibility that the practice has caused harm. Increasingly, veterinarians are recognizing the possible connection between viral vaccines and immune-mediated disease (Duval, 1996), (Kass, 1993), (Kelton, 1981), (Axhelm , 1987), and (HogenEsch, 1997). We know, for example, that yearly vaccines are associated with malignant tumors in cats. We suspect a connection between vaccines and autoimmune hemolytic anemia. Do we need more problems before we change a practice that we suspect to be unnecessary, anyway?

Alternatives to Yearly Vaccination

Please keep in mind that this section discusses alternatives to all vaccinations except rabies. Rabies vaccination is required by law in most states. Rabies can be an urban disease, frequently found in raccoons and foxes that raid suburban trashcans, and if your unvaccinated pet is exposed, the disease is invariably fatal. The majority of rabies cases in domesticated animals occur in cats.

One argument against vaccination has been that if we keep our animals perfectly healthy, feed raw diets, good water, and give them a perfect lifestyle, they will never succumb to these diseases when exposed. Many believe that this perfect lifestyle is simply impossible to achieve. Not much can be done about the air we breathe, although indoor cats that live with the luxury of multiple air filters may have an advantage here. It is well recognized that city water systems are far from "clean," as recent reports seem to suggest. Animals drinking distilled water may have a head start here. What about indoor air pollution? A recent review detailed the potential sources of indoor air pollution to which we are all subject, emphasizing that pets experience "comparable, if not greater" exposure to these pollutants, which may include nitrogen dioxide from gas appliances and water heaters, formaldehyde from foam insulation, and household cleaning agents. Of course, outdoor pets walk all over beautiful lawns full of chemicals, then walk into their homes to lick their feet.

Add to all of these insults the fact that purebred (and even mixed breed) animals may have genetic tendencies that can lead to greater susceptibility to these diseases and the potential for developing long term side effects from these diseases or the vaccines designed to prevent them. And we continue to hear of unvaccinated dogs and cats who die of these viral diseases. Because it is my belief that we cannot provide our pets with perfectly healthy environments and bodies (or even determine whether that is possible), it should be clear that we need to increase the odds in favor of our pets.

Nosodes

Nosodes may be one way to protect them; unfortunately, there is no convincing evidence that nosodes work. A few studies published in homeopathic journals suggest that nosodes may decrease the severity of active disease and possibly prevent the spread of epidemics, but these studies are not controlled. The results of one well controlled study suggest that parvovirus nosodes are completely ineffective in preventing parvoviral disease under experimental challenge conditions (Larson, 1996). Until well designed studies are completed and thousands of pet owners make a concerted effort to help with potential retrospective studies, nosodes remain an unknown quantity, and I do not recommend using them as a sole strategy for disease prevention.

I recommend that puppies and kittens undergo an initial vaccination series and that annual vaccination be continued for a year or two, depending on the individual. Unfortunately, many dogs and cats begin developing signs of allergy or other disorders early in life. It is not recommended that sick animals be vaccinated, and chronic illness may include the gamut of every day conditions like atopic skin disease, inflammatory bowel disease, or spondylosis. If we don't want to risk vaccination, and we don't know whether nosodes work, what next?

Titers

One strategy being used by many veterinarians is to test antibody levels in the blood of our pets. Antibody levels may suggest (but not conclusively prove) how much immunity that pet carries against a specific disease. For many diseases, antibodies are the prime source of protection against disease, and a high level suggests that the animal may adequately respond to the agent causing that disease. Conversely, low levels indicate that the pet may be susceptible to contracting the disease in question (an example is canine parvovirus). Unfortunately, antibodies tell only part of the story, and an animal may be perfectly immune to some diseases, but have low antibody levels to that disease (canine distemper may be one example). These antibody tests are not perfect indicators of immunity, and most immunologists suggest that we do not place total reliance on them. They are, however, the best tests we have, and can give the pet owner a rationale for not submitting a pet to vaccination, should there be any argument.

Many veterinary school diagnostic laboratories are capable of doing vaccine titers for your pet. Most private practitioners also have access to Antech laboratories, which will run an abbreviated test for a reasonable price. Some labs will set a threshold for protection, although others will only give the veterinarian a number, which must be interpreted in the light of experience. The serologic tests of interest for cats are IgG titers for feline panleukopenia, feline herpesvirus, calicivirus, and feline syncytial virus. We don't usually run titers for cats, but if this is done, panleukopenia is the only test that is meaningful. High titers to herpesvirus and calicivirus are too difficult to interpret since there are dozens of strains of these viruses. Feline coronavirus titers are measurable, but interpretation is very difficult and so these titers are not recommended. Cats are not tested for feline leukemia virus and immune deficiency virus by antibody levels, but by the presence of the virus. Dogs can be tested for parvovirus, coronavirus, herpesvirus, adenovirus, leptospirosis and distemper antibodies. We test for distemper and parvovirus only, as the other titers are either unimportant (coronavirus) or so short-lived that the information isn't often helpful (leptospirosis). Rabies antibody level tests are not offered or recommended in animals due to the public health implications (although human rabies titers are sometimes measured). We measure rabies antibody titers only for very sick or very old animals, such as those with cancer or life-threatening autoimmune diseases.

Practically speaking, dogs should have antibody titers against canine distemper and canine parvovirus evaluated. Canine hepatitis has been called an exotic disease, and since it is rarely seen today, titer assessment is probably unnecessary. The need for other titers, such as leptospirosis, should be evaluated according to the individual's general health and environment. Cats should have titers to feline panleukopenia tested. Be sure to advise the lab specifically of your interest in antibodies to vaccination. The lab should, in this case, change the normal testing technique by starting at lower serum dilutions to give a more accurate answer.

Once a number has been provided, how is this information interpreted? If the levels are in the "protective range" (understand that this is still a fuzzy number, due to the novelty of this technique in clinical practice), you can assume that the pet has made an adequate immune response to those diseases in the past. As wishy-washy as this statement may sound, this information is a much better indicator that the pet is protected than the simple act of vaccinating. Sticking a needle full of vaccine under the skin does not tell us that the pet is automatically immune—not all animals are genetically identical or live in identical environments. Scientists have no idea how each and every pet is going to respond to vaccination. Is the pet going to be protected by vaccination? No way to know for sure, but titers can help. If the titers look adequate, why vaccinate?

Sticky situations

For people who board their pets in boarding or veterinary facilities that require annual vaccinations, protective antibody levels actually provide more precise information about a pet's immune status than a simple history of receiving vaccinations. Animals receiving nosodes may or may not develop antibody titers, for reasons that would require pages more to explain. Suffice it to say that a nosode protected animal with sufficient antibody titers should still be considered adequately immunocompetent by facilities asking for this information, and for those animals receiving nosodes that do not develop titers, this rather inconvenient situation remains the same—one cannot prove the dog or cat is immune.

For pet owners whose veterinarians still insist on yearly vaccinations, I would carefully consider whether the pet is fully healthy or not. Allergies? Inflammatory bowel disease? Hypothyroid? These are illnesses, and sick animals should never be vaccinated. It says so, right there on the vaccine label.

Antibody titers are not going to save you any money, and they should still be done every 1-3 years, until we know how long these antibodies actually last in the blood. These annual tests will give us peace of mind, while at the same time helping to establish just how long vaccinations actually protect the average dog or cat. Knowledge of how to more safely and judiciously vaccinate our pets will save many thousands of pets unnecessary illnesses caused by our well-intentioned vaccine programs.

References and Further Reading

Appel M and Gillespie JH, 1972. Canine distemper virus, in Gard S (ed) Virology Monographs II, New York, Springer Verlag, pp 1-96.

Axhelm MK and Krakowka S, 1987. Canine distemper virus-induced thrombocytopenia. Am J Vet Res, 48: 1269-1275.

Carmichael LE, et al, 1981. A modified live canine parvovirus strain with novel plaque characteristics: I. viral attentuation and dog response. Cornell Vet J.

Cestmir A, Braciale TJ, Cernescu C, Doherty P, et al, 1995. The Experts Speak: How does a viral infection trigger an autoimmune disease? Viral Immunology, 8(4):187-192.

Day CEI, 1987. Isopathic prevention of kennel cough—is vaccination justified? Journal of the International Association of Veterinary Homeopathy, 2.

Dodds WJ, 1983. Immune Mediated Diseases of the Blood. Advances in Veterinary Science and Comparative Medicine, 27:163-196.

Duval D and Giger U, 1996. Vaccine-Associated Immune-Mediated Hemolytic Anemia in the Dog. J Vet Intern Med, 10:290-295.

Dye J and Costa D, 1995. A Brief Guide to Indoor Air Pollutants and Relevance to Small Animals. Current Veterinary Therapy XII. WB Saunders, Philadelphia, PA.

Ford, et al, 1995. Vaccines: Pioneering New Paths to Healthcare. Emerging Science and Technology: Advances in Veterinary Medicine. Fairway, KS.

Greene CE, 1990. Feline Panleukopenia, in Infectious Diseases of the Dog and Cat. WB Saunders, p 249.

Greene CE, 1990. Feline Panleukopenia, in Infectious Diseases of the Dog and Cat. WB Saunders, p 298.

Hogenesch H, et al, 1999. Vaccine-induced autoimmunity in the dog. Adv Vet Med, 41:733-47.

Kass PH, et al, 1993. Epidemiologic evidence for a causal relation between vaccination and fibrosarcoma tumorigenesis in cats. JAVMA, 203:396-405.

Kelton JG, 1981. Vaccination-associated relapse of immune thrombocytopenia. JAVMA, 245:369-371.

Larson L, Wynn S, and Schultz RD, 1996. A Canine Parvovirus Nosode Study. Proceedings of the Second Annual Midwest Holistic Veterinary Conference. Nov 2-3, 1996.

Olson P, et al, 1997. Distemper Titer study in Sweden 1995-1996. JVIM, 11(2):(abstract #178).

Phillips T and Schultz R, 1992. Canine and Feline Vaccines, in Current Veterinary Therapy XI. WB Saunders, Philadelphia, PA.

Saxton J, 1991. The Use of Canine distemper nosode in disease control. International Journal of Veterinary Homeopathy, 5:8.

Scott FW and Geissinger C, 1997. Duration of immunity in cats vaccinated with an inactivated feline panleukopenia, herpesvirus and calicivirus vaccine. Feline Practice, 25(4):12-19.

Smith C, 1995. Are we Vaccinating Too Much? JAVMA, 207(4):421-425.

Stopes C and Woodward L, 1990. The use and efficacy of a homoeopathic nosode in the prevention of mastitis in dairy herds: a farm survey of practising users. IFOAM: Bulletin of Organic Agriculture, 10:6.

Taylor SM, Mallon TR, and Green WP, 1989. Efficacy of a homoeopathic prophylaxis against experimental infection of calves by the bovine lungworm Dictyocaulus viviparus. Veterinary Record, 124:15.

Yamamoto K, 1994. Possible mechanisms of autoantibody production and the connection of viral infections and human autoimmune diseases. Tohoku J Exp Med, 173:75-82.