Vaccination

By Jean Hofve, DVM

Vaccination is a major controvery in veterinary medicine today. Veterinary schools and specialty organizations are promoting fewer vaccines at longer intervals, while many practicing veterinarians stubbornly cling to their annual booster schedules. What's the truth?

The Science Behind Vaccines

As a responsible cat caretaker, you probably visit the vet every year for your cat's check-up and "shots." But while an annual check-up is still vitally important for your cat's health, getting vaccines—how many and which ones—is a stormy controversy among veterinarians.

Until recently, vaccinations were considered harmless and beneficial. But today, scientific evidence proves that there are many potential side effects.

Most common vaccines are made using a "modified live virus" (MLV), which means that the virus is alive and can replicate in the animal's body, but has been modified so it does not cause disease, or at least not severe disease. This natural replication produces excellent, long-lasting immunity. However, some diseases are too dangerous to allow to replicate, or for some other reason the organism (whether virus, bacteria, or other parasite) must be killed to use in a vaccine. In that case, because the immune response is not as good, other agents, called "adjuvants," are added to the vaccine to stimulate a bigger immune response. The newest generation of vaccines includes recombinant vaccines that use only small fragments of the disease agent, which are inserted into a harmless carrier virus.

The purpose of a vaccine is to stimulate the body to produce antibodies (germ-fighting proteins made by specialized white blood cells) and "memory" cells, so that if the animal ever encounters the disease again, his system will be primed and ready to defend against it. It turns out that many vaccines are so good at this that they don't need to be boostered every year. The distemper and parvo vaccines for dogs, for instance, are believed to last at least three years. The feline panleukopenia (distemper) vaccine is even more effective; ongoing tests are showing good immunity for as long as eight years.

Most veterinary schools and several veterinary associations have studied the research, and concluded that annual boosters are unnecessary for most pets, and potentially harmful in some. They now recommend waiting three years between boosters for the most common dog and cat vaccines.

"Herd Immunity"

You might be surprised to know that the real purpose of vaccinations is not to protect your animal against disease, but to establish immunity in enough animals so that if a disease does break out, there will not be enough susceptible animals to sustain an epidemic. This is called "herd immunity" since the idea was first developed for livestock.

Because more and more people are not getting their animals (and often their children) vaccinated at all, herd immunity is weakening in many areas. Recent outbreaks of distemper in dogs and cats, and whooping cough and measles in children, are of great concern. No vaccines are just as dangerous as too many vaccines; the basic kitten and puppy shots (distemper, parvo and rabies) are still needed -- see "Recommendations" at the end of this article.

Annual Boosters: An Unnecessary Danger

Immunologically, annual boosters are totally unnecessary for the vast majority of animals. If a vaccine produces adequate antibodies, and those antibodies are still in the blood the following year, they will inactivate a booster, making it worthless as a protector, and potentially a danger.

Dr. Ronald Schultz at the University of Wisconsin is the premier vaccine researcher in the country. He says, that "canine distemper and adenovirus-2 vaccines both provide good lifelong immunity. These need not be given annually." He says the same about the feline distemper (panleukopenia) vaccine. He believes that a single dose of modified live vaccine given at 10-14 weeks of age is protective for life. Both canine and feline distemper vaccines have been shown to induce immunity for 5-7 years or more. Moreover, all of these are diseases of young animals; older animals are naturally more resistant. Once vaccinated, adult animals are typically fully immune.

The rabies vaccine is required by law for most animals in most jurisdictions. Therefore, it is important from a legal standpoint to follow your jurisdiction's regulations concerning rabies vaccines for your pets. Killed rabies vaccines are labeled for either 1 or 3 years; but the vaccine in the bottle is the same in both cases. Giving a 3-year vaccine every year puts your pet at even greater risk for an adverse reaction. If your pet receives a killed rabies vaccine, be certain that it is labeled for 3 years. For cats, there is a safer vaccine that does not cause cancer. Purevax, by Merial, is a recombinant vector vaccine that does not induce the inflammation that occurs with killed, adjuvanted vaccines. If your vet does not carry it, try to find one who does. It's worth it.

Risks Associated with Vaccination

There are several known risks that are associated with one or more specific vaccines.

Autoantibodies. Antibodies are the goal of vaccination. We want the body to produce antibodies against the disease being vaccinated against.

However, the vaccine manufacturing process contains some quirks that cause the body to make antibodies to a wide variety of components in the vaccine. Most vaccines are produced from some type of culture. The culture medium may be blood serum or certain types of cells. The organism is grown in these nutritious cultures, then filtered for manufacture into vaccines.

Unfortunately, while the filters are small enough to keep out whole cells, both viruses and a variety of loose proteins will end up in the final product. When injected, the dog or cat's body then makes antibodies to many of the proteins as well as the virus itself. Studies at Purdue University showed that canine vaccines grown in calf serum caused antibodies to be made to many calf proteins including red blood cells; thyroid; DNA; connective tissue proteins such as collagen, fibronectin, laminin, albumin, transferrin; and others.

Unfortunately, calf proteins are so similar to dog proteins that the antibodies react to the dog's own tissue as well-—this is an "auto"-immune reaction ("auto" means "self"). Every vaccinated puppy developed multiple autoantibodies (antibodies to its own tissues), and every additional booster caused even more autoantibodies to be made.

Because the puppies in this study were euthanized at 22 weeks of age, it is unknown if or how often these autoantibodies would lead to disease, but follow-up studies with client-owned dogs are ongoing.

Diseases associated with the tissues to which autoantibodies are made include thyroiditis (which typically leads to hypothyroidism in dogs), lupus, cardiomyopathy, and autoimmune hemolytic anemia.

Chronic Renal Failure (CRF).

The common feline distemper (panleukopenia) virus is grown in a culture of feline kidney cells. Recent work at Colorado State University showed that most kittens developed autoantibodies to their own kidney tissues after being vaccinated for distemper. When autoantibodies react with body tissue, the result is inflammation. Each booster vaccine creates even more inflammation. Chronic low-grade inflammation is the primary cause of CRF, which is almost guaranteed to develop in older cats. The authors of the study suggest a causal relationship between the distemper vaccine and the development of CRF. In other words, annual re-vaccination for feline distemper may be a major cause of death in older cats. Annual boosters for feline distemper are totally unnecessary because the immunity produced by the initial kitten vaccines is so long-lasting.

Vaccine-Associated Sarcomas (VAS)

Many people have heard about the malignant, fatal tumors called fibrosarcomas that can be caused by some vaccines in cats. This cancer occurs in the connective tissue. Research in dogs shows that vaccines cause autoantibodies to be made to many connective tissue components. The two vaccines currently implicated are rabies and feline leukemia. A third may be joining the list soon — the new feline AIDS (FIV) vaccine. What do these three products have in common? They are all "killed" vaccines that are made with adjuvants to increase the body's response to the vaccine. Unfortunately, in cats, this additional response includes inflammation that can lead to the formation of cancer. Even worse, every additional vaccine — indeed, some researchers suggest that every additional injection of any kind (antibiotics, steroids, fluids, etc.)— may significantly increase the risk of developing cancer, particularly if the injections are given in the same place. Merial is working on non-adjuvant vaccines for feline leukemia and FIV; some have already been introduced in Europe.

The incidence of VAS is at least 1 in 10,000 cats, and some studies suggest it may be as high as 1 in 1,000 cats. Let's think about that number for a minute. There are 77 million cats in U.S. homes today; so between 77,000 and 770,000 of them will be diagnosed with a fatal cancer caused by vaccination. There appears to be a genetic or heritable susceptibility to this cancer, but there is no way to check for this genetic defect. What if one of those cats is yours?

When vaccines were given between the shoulder blades, these cancers were inoperable because they would grow into the spine, ribcage, and chest. This became such a serious problem that now it is recommended to give the rabies vaccine low in the right hind leg, and leukemia low in the left hind leg — so that when a tumor does develop, the whole leg can be amputated and thus the cat's life can be saved. I guess the FIV vaccine will have to be given in the tail, the next most likely appendage to lop off in the event of cancer.

Titer Testing to Assess Immunity

A "titer" measures antibodies in the blood for a specific disease. Basically, the blood is diluted, then incubated with a marker of the disease (proteins from a virus, for instance); if antibodies are present, they will react with the marker and produce a positive titer. The most extreme dilution at which the reaction is seen is notated. For example, there may be a reaction to the distemper virus at a dilution factor of 1:1200, which would be a strong positive.

Titers have gained some acceptance as a guideline on whether an animal needs a booster vaccine. For instance, if your cat had a high titer to distemper, there would be no need to give a distemper booster. There is a growing body of scientific evidence that most viral vaccines produce high, long-lasting titers in most animals.

However, while titer tests are available for many common diseases, there is no consensus on how high a titer is protective for each disease. For example, a positive rabies titer of 1:2 is very low and would not be acceptable as proof of immunity to rabies. (In most jurisdictions, titers are not legal proof of rabies immunity and even a high titer will not exempt the animal from vaccination for rabies as required by law.) While low or borderline titers are open to interpretation, most experts agree that a high titer indicates good protection from the disease.

Additionally, a titer measures only one facet of immunity, circulating antibodies. When a vaccine is given, antibodies are produced by the lymphocytes, but in addition to antibodies, particular lymphocytes called "memory" cells are produced. These memory cells live quietly in the lymph nodes until such time as there is another exposure to their particular disease. These memory cells then "jump-start" antibody production, so that the reaction is much faster and stronger than it would be if the body had never "seen" the disease before.

Also not measured by a titer is the animal's "cellular immunity." This involves T-lymphocytes that directly attack and kill viruses, bacteria, and other invading organisms. This is another "first line" immune response; it starts immediately and keeps going while the body produces enough antibodies to take over and clear the infection.

If you wish to minimize your pet's vaccines, but want to know – to the extent possible – whether or not she is protected against disease, it may be worthwhile to have your veterinarian run a titer test. It is not perfect, but it does provide a snapshot of at least one important part of the immune system.

Recommendations

Experts agree that only panleukopenia and rabies vaccines are a must for all cats. All other vaccines are optional, and should only be given if the cat's lifestyle or health considerations make them necessary. Indoor cats do not need vaccines against Feline Infectious Peritonitis (FIP), Giardia, Ringworm, Bordatella, or Feline Immunodeficiency Virus (FIV, feline AIDS)— even if the cat accidentally gets out, the risk of these diseases is extremely remote.

An initial two- or three- vaccine series for kittens is necessary for most vaccines to be effective. Vaccines should be given at least 3 weeks apart; there is little published research suggesting an outside limit, but a 4-6 week interval is probably safe and effective.

The initial panleukopenia (feline distemper)/rhinotracheitis (feline herpesvirus)/calicivirus vaccine (with or without Chlamydia) can be given at 8-9 weeks of age, followed by a booster at 12-14 weeks and at 1 year. However, according to immunology researcher Dr. Ronald Schultz at the University of Wisconsin, older kittens and adult cats of unknown vaccination status will be protected by a single vaccine, regardless of prior history. Many protocols now suggest re-vaccination for panleukopenia every 3 years, but even this is probably overly cautious. Given the potential for this booster to contribute to the development of chronic renal failure, minimal re-vaccination seems wise.

The vaccine for Feline Leukemia is more controversial. While clearly unnecessary for totally indoor cats, there is some concern that if a cat does not remain in its original home for life, at some point it could be exposed to the virus. Feline leukemia is not an easy disease to get. It generally requires close, prolonged contact for transmission. Most cats who are exposed will clear the virus by the action of their own immune system. Because it is primarily (though not exclusively) a disease of younger cats, some experts suggest that kittens should receive the initial series of two leukemia vaccines to protect them during the most susceptible period, then never again. The vaccine is not 100% protective, and because it is a killed virus, it does carry the risk of tumor formation at the injection site.

Rabies vaccination is required by law in many states and municipalities. Check with your local animal control to find out what is needed in your area. Ideally, the Merial Purevax recombinant vaccine can be used in place of the older killed vaccines that can cause injection-site tumors.

Vaccination is a medical procedure with risks and benefits. Ask your veterinarian what the purpose of each recommended vaccine is, why your cat should receive it based on its current health, lifestyle, and risk factors, and what the potential adverse effects are. Become an active partner in your cat's health!

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SpiritEssence offers a Vaccine Detox remedy that helps disperse the toxic energies that can be introduced into the body by vaccines. Check under your pet's species in the "Health Remedies" section!