By Jean Hofve, DVM
Reprinted with permission.
"Indoor cats do not
|Vaccination is an ongoing controversy
in veterinary medicine today. Veterinary schools and specialty organizations are
promoting fewer vaccines at longer intervals, while many practitioners
stubbornly cling to their annual booster schedules. Who's right, and what's the
The Science Behind Vaccines
As a responsible pet caretaker, you probably take your animal companion to the vet every year for a check-up and "shots." You probably get one or more reminder postcards about it! But while an annual check-up is still vitally important for your pet's health, vaccination—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 harmful 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 more vigorous 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.
"Given the general
resistance of adult
animals to viral
infection, plus the
potential for the feline
to contribute to the
development of chronic
renal failure, minimal
re-vaccination, if any,
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, if at all.
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.
You might be surprised to know that the real purpose of vaccinations is not really to protect your particular 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 can be 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.
Vaccination is a
with risks and benefits.
Ask your veterinarian
what the purpose of
vaccine is; why your
should receive it—
based on current
health status, lifestyle,
and risk factors; and
what the potential
adverse effects are.
Make sure that every
vaccine is well justified,
and don't let anyone
bully you into complying
with their clinic's
outdated or inflexible
Don't give multiple
vaccines at the same
time; space them out at
least 3 weeks apart. You
have the information;
now you must become
an active partner in
your pet's health!
Annual Boosters: An Unnecessary Danger
Immunologically, annual boosters are totally unnecessary for the vast majority of animals. The way the immune system works, a vaccine does not suddenly lose its effectiveness a year and a day after the last shot, although some veterinarians imply that being even a tiny bit late for a booster is putting your animal at grave risk. It's just not true. If a vaccine produces adequate antibodies, and those antibodies are still in the blood the following year, they will actually inactivate the booster, making it worthless as a protector, and potentially a danger. Additional vaccine doses in an immunized animal do not increase or improve the immunity, but they do increase the risks.
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 3-8 years or more. Moreover, all of these are diseases of young animals; most older animals are naturally 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 exactly 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: Purevax, by Merial, is a recombinant vector vaccine that does not induce the inflammation that occurs with killed, adjuvanted vaccines. If your vet clinic does not carry it, ask if they will order it, or try to find one who does. It's worth it.
Rabies is a serious disease, and 100% fatal (with the exception of one young
woman that has never been duplicated). Cats are frequently infected. Even indoor
cats need to be protected from rabies; bats can get into attics, come down
chimneys, or enter through windows; in one case, a cat caught a bat on the
balcony of his 14th floor apartment in downtown Denver. There are serious legal
liabilities as well, with life-threatening potential for your cat apart from the
disease. Rabies vaccines provide long-lasting protection if given properly to
If your pet has a chronic disease or is for any reason not completely healthy, it should NOT be vaccinated. All vaccines carry a label that states "for use in healthy animals only." Many jurisdictions will accept an exemption letter from your veterinarian attesting to the fact that your pet is at high risk and cannot be vaccinated.
Risks Associated with Vaccination
Several known risks 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 through a culture medium such as eggs, blood serum, or certain types of cells. The organisms are grown in these nutritious cultures, then filtered for manufacture into vaccines.
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, and
every additional booster produced even more autoantibodies. Because the puppies
in the Purdue study were euthanized at 22 weeks of age, it is unknown if 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 can leads to hypothyroidism in dogs), lupus, cardiomyopathy,
and autoimmune hemolytic anemia.
Titer Testing to Assess Immunity
A "titer" measures antibodies in the blood for a specific disease. 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 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 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 been exposed to 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.
Experts agree that only "core" vaccines—panleukopenia and rabies for cats, and distemper/parvo and rabies for dogs—are truly necessary. All other vaccines are optional, and should only be given if the animal's lifestyle or health considerations make them necessary.
Indoor cats do not need vaccines against Feline Infectious Peritonitis (FIP), Giardia, Ringworm, Bordatellaor Feline Immunodeficiency Virus (FIV, also called "feline AIDS"). Even if cats do go outside (something I don't recommend!), the risk of contracting these diseases is very small.
Dog vaccines available include several that are worthless or dangerous. Coronavirus, Giardia, and Ringworm vaccines either do not prevent disease, or the disease is so mild as to not be worth vaccinating for. Rattlesnake, Bordatella (kennel cough), and Leptospirosis should only be given to high-risk animals or when required, such as for show dogs or boarding kennels. Leptospirosis is becoming more common throughout the U.S.—although the vaccine is not 100% effective, and causes some of the most severe reactions. Dogs in limited areas of the northeastern U.S. may need the Lyme disease vaccine.
An initial two- or three- vaccine series for kittens and puppies 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 at least a 4-8 week interval is probably safe and effective. The animal should be at least 8 weeks of age before vaccinating. The common breeders' practice of vaccinating pups at 2 weeks of age and then every 2 weeks is useless, not to mention harmful to young puppies' immune systems.
The initial canine distemper/parvo/hepatitis/parainfluenza or feline panleukopenia–rhinotracheitis (feline herpesvirus)–calicivirus vaccine can be given at 8-9 weeks of age, followed by a booster at 12-14 weeks and, if desired, 1 year later. However, according to immunology researcher Dr. Ronald Schultz at the University of Wisconsin, older kittens and puppies, and adults of unknown vaccination status, will be protected by a single vaccine, regardless of prior history. Many protocols now suggest re-vaccination for distemper/parvo or panleukopenia every 3 years, but even this is overly cautious. Given the general resistance of adult animals to viral infection, plus the potential for the feline panleukopenia vaccine to contribute to the development of chronic renal failure, minimal re-vaccination, if any, seems wise.
Cat vaccines pose a particular problem due to the feline tendency to develop cancer. Feline Leukemia is not very contagious, and adult cats are naturally resistant. Some experts suggest that kittens should receive the initial series of two vaccines to protect them during the most susceptible period, then never again. FIV is a killed vaccine, so will undoubtedly cause vaccine-associated cancers just like the rabies and leukemia vaccines. Additionally, there is no way to tell a cat with a real infection apart from one who is vaccinated. A vaccinated cat that gets lost or for some other reason ends up in a shelter will test positive for FIV and may consequently be euthanized. I do not recommend either one.
Rabies vaccination is required by law in many states and municipalities, and must be up-to-date to transport animals from state to state. Check with your local animal control to find out what is needed in your area. Ideally, for cats 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 animal companion should receive it—based on current health status, lifestyle, and risk factors; and what the potential adverse effects are. Make sure that every vaccine is well justified, and don't let anyone bully you into complying with their clinic's outdated or inflexible protocols. Don't give multiple vaccines at the same time; space them out at least 3 weeks apart. You have the information; now you must become an active partner in your pet's health!
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