Are We Vaccinating Too Much?
By Elizabeth Colleran, D.V.M.

From Animal Issues, Volume 29, Number 3, Fall 1998

In 1978, puppies and dogs began to die. Suddenly, they began to vomit and have diarrhea. Often, both activities were bloody. Puppies rapidly became dehydrated and died. No one knew right away what caused it, but a pandemic began. The search also began for an explanation.

Serious illness and often death occurred in all ages of dogs. Puppies under six months, however, were most affected. Outbreaks occurred all over the world. A virus called Canine Parvovirus (CPV) was identified as the source of infection. Yet, studies indicated that the virus had not existed inside the United States prior to 1978. Still hundreds of puppies were dying.

Investigators realized that there were similarities between this virus and a feline virus called Panleukopenia. The vaccine that prevented infection with this virus also protected puppies against Parvo (CPV). The search for a safe and more protective vaccine for puppies began. By 1981, the Parvo virus vaccine was thought to be both. It was integrated into routine vaccinations for puppies and adult dogs.

Present estimates of the presence of the virus in dog blood samples vary from 20% to 60%, depending geography and other factors. Certain breeds are more susceptible to the virus, particularly Rottweilers and Dobermans. Crosses of these breeds and others have been more likely to become sick despite vaccination or to become more seriously affected by the virus. Puppy vaccination schedules vary, but all have integrated multiple frequent "boosters" against Parvovirus along with other vaccines. The reward for this effort has been infrequent infection in protected puppies and far fewer deaths. Clearly, this vaccine has been an important addition to veterinary preventive medicine.

Fibrosarcomas

Yet, the use of vaccines is not always this clearly beneficial. In 1991, Dr. M. J. Hendrick wrote a letter to the editor of the Journal of the American Veterinary Medical Association (JAVMA) asking, "Do injection site reactions induce fibrosarcomas in cats?" Hendrick, a pathologist, had noted an increase in inflammatory reactions and fibrosarcomas, an often deadly type of tissue cancer, in feline biopsies. From 1987 to 1991, she documented a 61% increase in this cancer, the majority occurring in sites used for vaccinations in cats. This time frame corresponded to significant changes in vaccinations and vaccination policies for cats.

Rabies vaccine was altered so that it could be given "under the skin" rather than "in the muscle," to decrease discomfort. The vaccine was also made more potent so that it could be given at 3-year intervals. In addition, many states enacted mandatory feline rabies vaccinations. At about the same time, Feline Leukemia (FeLV) vaccines were created and then altered to be given "under the skin" or subcutaneously. Subcutaneous vaccines must be 100 times more potent than those given in muscles in order to be effective. These vaccines were intensively marketed.

Since that initial letter, studies have further supported the link between these and other vaccines and the incidence of soft tissue cancers at the site of vaccination. Other studies have shown that the risk increases with the number of vaccines given at the same location on the body. The estimated incidence of these cancers remains low, however, at about 1 tumor per 10,000 vaccines given. No particular vaccine, vaccine ingredient, or vaccine manufacturer has emerged as the culprit.

Inducing Immunity

Vaccines induce immunity to disease by stimulating a healthy immune response. A virus that causes disease is killed or otherwise modified. The new version looks just like the old one to the body, it just won't do as much harm. The immune system targets this enemy and mounts an immune response involving very sophisticated weapons. Later, if the virus that causes disease is encountered, the body is ready for it. A powerful immune response successfully fights it off using the weapons that have been prepared by the vaccine.

A local reaction to the vaccines is widely thought to begin the process of immunity. It is thought that this local inflammation transforms itself on rare occasion into cancer. Studies continue and theories are numerous.

In addition, this work has encouraged further investigations into the relationships between vaccines and other chronic illnesses such as arthritis, diabetes, autoimmune disease, and thyroid problems in both dogs and cats. Many veterinary medicine investigators, including epidemiologists and virologists, believe that the incidence of adverse reactions to vaccines, from minor to severe, is increasing

Presently, though the details vary, most veterinarians advocate a standard protocol of vaccinations for cats and dogs. A series of puppy and kitten vaccines usually beginning at 8 to 10 weeks is composed of a variety of virus components. Rabies is usually given at about 4 months of age. One year later these vaccines are repeated, followed by annual vaccinations from then on.

The mix of components of vaccination differ (as does the timing) by practice, region, and incidence of the virus in the area. The first piece of the puzzle is to know what viruses are in the vaccines and why. Canine vaccines may contain as many as 7 components. Feline vaccines often have 4, 5, or 6. Canine protocols may include, in addition to the combination vaccines, Parvo virus alone, Lyme, Bordatella, and Rabies. Feline schedules may include Chlamydia, FeLV, FIP, "Ringworm," and Rabies. With the single exception of Rabies, none of these vaccines are always indicated. Within the combination vaccines may be virus components that need not be there as well.

No Sound Science

Another piece of the vaccination story is that there is no sound science behind the use of annual vaccinations after the first year. Vaccine manufacturers will say that the prevention of disease is more important than the occasional adverse reaction. They will also state emphatically that the use of a certain type of indicator of immunity is inadequate.

This measure of immunity is called "antibody titer." This is a test of the amount of protective immunity that exists in blood in the form of antibodies to the virus. It does not provide perfect information about how the body would respond if it were challenged by the virus. It does, however, give a partial indication of level of immunity.

The perfect study would vaccinate animals that were carefully protected and then challenge them with the virus that causes disease. Multiple challenges over time would be necessary to give absolutely reliable information about immunity. Each virus would have to be tested separately. Doubtless these tests would be a terrible idea for anyone who loves animals.

One would logically then inquire about the way in which vaccines are tested in human children and how intervals between vaccination are determined, since these same tests would be the standard for determining immunity. The answer is that in human medicine antibody titers are used. In addition, the principles that are known to govern immunity, the incidence of the disease, and the judgments of specialists are included in the decisions about what and when to vaccinate children. For example, a study of the levels of' immunity to polio virus among inner-city children used antibody titers to conclude that immunity was high and directly related to the number of doses of polio vaccine received.

Others studies show that children vaccinated for measles, mumps, and rubella have protective titers at 11 and 13 years of age. There is no evidence that the immune system of the cat or dog is inferior to that of humans.

In a study of Distemper virus in Sweden, 83% of the 95 dogs who had not been vaccinated for Distemper in over 4 years had a protective titer. A duration of immunity study in cats vaccinated for the 3 most common upper respiratory viruses demonstrated immunity that lasted at least 3 years. These studies used antibody titers as a measure of immunity because a strong association between titers and immunity has been established by many laboratories.

A Key Aspect

One spokesperson for a vaccine manufacturer insists that annual vaccination has effectively prevented disease and thus should not be changed. He called the advice of those in the veterinary community who called for change in frequency of vaccination "the theoretical views of the academic." He also reminded the reader that duration of immunity studies would be expensive. This cost, he said, "will be borne by the pet-owning public." Finally, he reminds the practitioner that the animal health companies have been "key in providing the products vital to a successful practice." These remarks illuminate a key aspect of the controversy over annual vaccinations: money.

As of 1996, the greatest percentage of revenue in veterinary private practice came from vaccines. Though recent studies have shown that the percentage of revenue from vaccines is falling, it is still about 13%. The vaccine manufacturers heavily market their vaccines and are dependent upon this revenue stream. Many "high volume/low price" clinics rely very heavily on this source of income. "Shot" clinics are everywhere. If it was no longer considered advisable, based upon new information, to vaccinate for all these viruses annually, what would be the impact on these segments of the veterinary population? Needless to say, the controversy continues to rage on.

New Guidelines

JAVMA has been one of the most vocal forums of debate among veterinarians. In January 1998, JAVMA published new guidelines for vaccinations in cats by the American Association of Feline Practitioners (AAFP) and the Academy of Feline Medicine (AFM). (For a useful table from the guidelines, click here. For the entire report [115 KB], click here.) Ten months in preparation, this document has prompted an ongoing debate in letters to the editor.

Veterinarians opposed to these new guidelines raise some legitimate points. They call it premature because the challenge studies described earlier have not been completed. One writer called it "radical," complaining that with these guidelines cats "will receive less attention," and describing this as "negativism about overvaccination." Another writer stated he "believed that the AAFP/AFM guidelines will cause much more harm than it [sic] will prevent."

The response from the committee reminds veterinarians that annual revaccination is not based upon sound science. Vaccine manufacturers are not required to evaluate vaccines, with the exception of rabies, for more than a few weeks or months. Moreover, several veterinary schools have already changed their protocols given the current information on duration of immunity.

Raising the Question

In 1995, in a column called "Current Concepts," JAVMA published a commentary entitled "Are we vaccinating too much?" In it several experts in the areas of epidemiology and virology discuss what is known and not known about immunity to diseases and vaccination.

Dr. Fred W. Scott, professor of virology and chair of the Cornell Feline Health Center, stated that good titers to 2 of the 3 upper respiratory viruses were found 3 to 4 years after vaccination at 12 weeks.

Dr. Ronald D Schultz, professor and chair of the department of Pathobiological Science at the University of Wisconsin, said he didn't think there was a need to vaccinate adult dogs against Parvo virus since early vaccination will be sufficient. He also stated that there was no need to vaccinate for Corona virus or Lyme disease since both diseases are rarely diagnosed.

These and other experts raise important issues that need to be addressed. For example, little is known about duration of immunity to Feline Leukemia Virus (FeLV) and Feline Infectious Peritonitis (FIP). Both are considered deadly diseases if they are contracted. They remind us, too, that though there are no final data linking immune mediated diseases in dogs and cats, there is this link in some specific human diseases and vaccines.

The article's contributors also warn that the use of multiple components in a single vaccine may be linked to vaccine failure. The more virus components in a single vaccine the higher the likelihood for an abnormal immune system response that could cause organ damage, as well. It is also more likely that a local response like tumor formation will occur with multiple vaccines given on the same location. Finally, they describe a higher incidence of vaccine induced disease in certain breeds or specific families.

All of this must be balanced with the knowledge that significant diseases have been vastly reduced in frequency with the use of canine and feline vaccination schedules. Another major benefit of annual vaccines has been the annual physical examination, if it was given. Doubtless, going to "shot clinics" eliminates this benefit. Nonetheless, if an animal is examined regularly, the early detection of problems or diseases gives a much better opportunity for successful treatment. Most of these exams have been the direct result of annual reminders to vaccinate.

Indeed, in general, it can be said that the benefits of vaccines outweigh the risks in many respects. But the one cat who develops a cancer at the site of vaccination or the dog who acquires an immune system disease is 100% affected, despite the low percentage of risk.

Research Needed

Much more research is needed. New vaccine development is underway to create safer, more effective vaccines. Further understanding of the association between certain diseases and vaccination is also key. Meanwhile, there is much the caretakers of dogs and cats can do to understand and participate in their healthcare.

A recent study, published in 1997, showed that only 27% of clients knew about some of the components that were included in annual vaccine regimes. As a caregiver, it's important that you know what the patient is being vaccinated for and why. For example, many feline vaccines combinations contain Chlamydia which is generally thought to be unnecessary. Corona virus is often included in the canine combination vaccine, also thought to be inessential.

Ask your veterinarian what viruses are considered important in your region. If Lyme disease does not occur, don't vaccinate for it. Understand that there are risks associated with behavior and environment. Outdoor or inside/outside cats are at risk, in many areas, for Feline Leukemia virus (FeLV). Protective vaccination, at this point, is thought to be necessary annually. Feline Infectious Peritonitis is thought to be a disease of multiple cat households and catteries. Prevention and eradication of this disease is thought to be more useful than the currently available vaccines.

Several veterinary schools, including Colorado State and University of Wisconsin, have changed their vaccine recommendations to reflect the current thinking about duration of immunity and risks. Colorado State's are on its web site at www.cvmbs.colostate.edu/vth/savp2.html. You may wish to discuss these with your veterinarian.

The AAFP/AFM feline vaccination recommendations are also readily available as a tool to help you communicate with your veterinarian. Call the AAFP at 505-343-0088 for a hard copy of the guidelines, or click here for API's Web version.

Ultimately, the decision is yours to make about vaccinations as well as other healthcare decisions. These should always be made on the basis of the most sound information available, the judgment of your veterinarian about the health status of the dog or cat, and your shared evaluation of lifestyle, age, genetics, possible exposure to other animals, and regional differences.

More important than any vaccine decision is a regular healthcare plan that includes at least an annual physical exam. It is worth remembering that dogs and cats age far more rapidly than humans so an annual checkup is far less frequent for them than for you.

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Recommended Guidelines for Vaccination of Cats

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Other Approaches to Vaccinations

Recognizing that research has yet to establish the validity of the latest vaccination guidelines, some caregivers prefer to seek alternatives for their companion animals. Whichever you choose, API urges you to check with your own veterinarian before embarking on any other remedies.

Holistic alternatives replace vaccinations with homeopathic remedies called nosodes. Nosodes are made from naturally occurring disease products. Distemperinum, for example, is a nosode made from the secretions of a dog that has been exposed to and is sick from distemper.

To manufacture nosodes, a sick animal's secretions are diluted, sterilized, and carefully prepared in accredited pharmacies. If properly administered, this solution can adequately protect a dog from distemper.

If you wish to use nosodes successfully in place of traditional vaccines, you must seek the advice of a holistic veterinarian. Contact the American Holistic Veterinary Association at 410-569-0795 for referral to a holistic veterinarian in your area.

In his Complete Guide to Natural Health for Dogs & Cats, Dr. Richard Pitcairn, an expert in the field of holistic veterinary medicine, suggests a modified vaccination plan that includes:

using single or simple vaccines instead of complex vaccines (ideally, this means vaccinating for one disease at a time rather than a multitude of infections at once);
where possible, using only "killed" or "inactivated" vaccines (as opposed to "modified live") (these "killed" vaccines cannot grow in the body and cause infection and are generally safer to use).
A wealth of information on these and other alternatives is also available on the Web at http://www.geocities.com/~kremersark/newhope.html. Again, these are suggestions only. Before you make your decision, consult with your veterinarian.