Vaccination Decisions

by Susan Gayle Wynn, DVM

Conventional veterinary wisdom states 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. Vaccinations have certainly worked to decrease the incidence of acute viral disease, but many pet owners and some veterinarians have begun to question both the need for annual, life-long re-vaccination, as well as the long term consequences of vaccination in general.
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 bacteria and viruses lasts years, and the only exception to this rule is immunity to bacterial toxins, such as tetanus toxin (necessitating yearly boosters for horses, for example).
Dr Schultz has 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.
Most recently, 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.

Alternatives to 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 students of environmental medicine believe that this perfect lifestyle is simply impossible to achieve. There is not much that 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 be given 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. 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 may be one way to protect them; unfortunately, there is no convincing evidence that nosodes do prevent disease. 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 well controlled. The results of one recent well controlled study suggest that parvovirus nosodes are completely ineffective in preventing parvoviral disease under experimental challenge conditions. 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?
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. 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.
Currently, there are three laboratories in the country which test for these antibodies, but more are coming on board with time. 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 are IgG titers for feline panleukopenia, feline herpesvirus, calicivirus, and feline syncytial virus. Feline coronavirus titers are measurable, but interpretation is difficult, so most veterinarians only use this test if clinical FIP is suspected in a sick cat. Dogs can be tested for parvovirus, coronavirus, herpesvirus, adenovirus, and distemper antibodies. Cats are not tested for feline leukemia virus and immune deficiency virus by antibody levels, but by the presence of the virus. Rabies antibody level tests are not offered or recommended in animals due to the public health implications (although human rabies titers are sometimes measured).
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 unecessary. 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, herpesvirus, and calicivirus 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 certain indicators suggest that the pet has made an adequate immune response to those diseases. 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. Since 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 except to do antibody titers. If the titers already look adequate, why vaccinate?
For people who board their pets in facilities which 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 anything.
Antibody titers are not going to save the pet owner any money, and they should still be done annually, 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 iatrogenic illnesses.


W J Dodds (1983). Immune Mediated Diseases of the Blood. Advances in Veterinary Science and Comparative Medicine 27:163-196.

T Phillips and R Schultz (1992). Canine and Feline Vaccines, in Current Veterinary Therapy XI, W B Saunders, Philadelphia, PA

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

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

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

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