injection-519388_1280Vaccination 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 truth?

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.

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.

“Herd Immunity”

You might be surprised to know that the real purpose of vaccinations is not only 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.

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 young animals.

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 leadsto hypothyroidism in dogs), lupus, cardiomyopathy, and autoimmune hemolytic anemia.

Feline 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 antibodies—and 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 the 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 will no doubt join the list—the feline AIDS (FIV) vaccine. What do these three products have in common? They are all killed vaccines spiked with “adjuvants” (compounds that increase the immune system’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, FIV, and other diseases.

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 90 million cats in U.S. homes today; so between 90,000 and 900,000 (almost a million!) of them will develop a fatal cancer caused by vaccination. There may be a genetic 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 in the right hind leg, and leukemia 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, so it too can be whacked off in the event of cancer.

Recently, the same vaccine-associated tumors have been reported in both dogs and ferrets. While these species are more resistant, obviously they are not immune.

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 (preferably 9) 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.

Chlamydia is an uncommon cause of respiratory infections in cats, which are usually due to feline herpesvirus and/or calicivirus. The Chlamydia vaccine does not prevent infection; and at best reduces (but does not eliminate) symptoms and viral shedding. Like most bacterial vaccines, it requires two shots to be of any use; it does not produce long-lasting immunity; and it carries a higher risk of adverse reactions. It is neither necessary nor recommended.

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!

With the upcoming–and completely fabricated–Swine Flu Epidemic on the horizon, there is fear among many that the American people will be “force-vaccinated.”  Knowing what we know about vaccines, this is a serious threat. Yet there are steps that you can take to protect yourself and your family from the damaging effects of vaccines. Click here for more information.



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15 comments for “Vaccination

  1. catdivine
    September 17, 2014 at 10:19 am

    My vet required my 3 year old cat to have a rabies vac before teeth cleaning. He had not had rabies vac except as a kitten. Is there any danger of tumor growth with just this one booster? That was the only vaccine required by the vet. He did tell me it was a 3 year vaccine.

  2. inmyveganopinion
    May 18, 2012 at 2:47 pm

    I am so livid right now, my cat has kidney problems and has for about 3 years and the vet (banfield) gave her vaccines 3 weeks ago, they didnt even ask me they just did them since it was part of the wellness plan I have. They KNOW she has kidney problems and they still gave it to her! She got a bad UTI 1 week later. Its sad .. they could potentially kill my cat and I have zero recourse.

  3. Joan
    January 12, 2012 at 8:29 pm

    Hi – Does anyone feel differently about the PureVax Vet Jet FeLV vaccine than traditional ones? We have 3 healthy 9 mo. old kittens and just picked up a stray that we’d like to keep. He tested neg for FeLV, but I’ve heard many stories of it “shedding” later. To protect everyone to the fullest we are considering the Vet Jet. Otherwise, our vet said to separate them for 6 MONTHS and retest new guy then! Killed FeLV vaccs have a high rate of VAS, but does the Vet Jet considerably lower the risks? BTW – I do not plan on vacc’ing at all after the “kitten series”.

  4. Judy
    November 2, 2011 at 12:31 am

    I learned about Purevax on your website about four years ago and called around to see who provided it. Most of the vets had it or agreed to order it. The one they received the first Purevax vaccine from said it was the only one they had. Unfortunately I moved since and the clinic is too far away to go to anymore. The Vet Clinics in my area now either have access to it or have it. My current Vet unfortunately disagreed with me, and tried to talk me out of it. I am not sure how long I will stay there. I was told when I expressed my fear of giving any vaccinations, that they, my cats, could be taken away from me if I refused vaccination! That really felt terrible at the time. My cats are seven years old. I did miss one year of Rabies but not intentionally. I have refused any other vaccination. Of course I did agree to be current with the rabies. I had dentals done for both this week. Right now they both have growths being evaluated. One was found when taking blood and removed from the inside of my cats leg leaving quite a long scar. The other has a growth on her eyelid. It really saddens me since I lost two dogs at the exact age of seven from cancer. One had it in the lymph nodes and the other’s was a rapid growing cancer of the bladder. Of course nobody knows what they were from but I agonized for so long as to what I might have done wrong. It was heartbreaking as anyone knows. I wish someone could do something about this. Thank you for your website and for truly caring about our pets. Keep up the good work and providing good information. Sincerely, Judy

  5. jhofve77
    September 7, 2011 at 10:25 am

    Oh, gosh, I am so sorry to hear about your poor kitty and his sad story! Hopefully others will learn from your experiences and think twice (maybe more than twice!) about loading their cats up with unnecessary vaccines! The veterinary profession has such enormous inertia on this subject; we’ve known about these tumors for nearly 20 years, yet so many vets keep vaccinating every pet with every vaccine every year (does this sound familiar, Banfield?), causing untold harm and suffering!

  6. Shelle deJongy
    September 5, 2011 at 11:55 am

    I suggest to everyone that you seriously consider the vaccines necessary and what holistic and adjuvent free choices are available before you vaccinate! I listened to my vet and gave the required vaccines and am now learning a tough lesson the hard way.

    My 15 year old beautiful boy persian kitty (indoor cat) developed cancer from a vaccine (VAS.) We have been battling it with surgeries, (4 infact)removing the tumor from his hind leg. The cancer has now won and metastasized into his body taking over his lungs, spleen and basically spread throughout his body.

    I feel I will never forgive myself for being ignorant and letting him receive vaccinations. It is extremely painful watching him go from a 12 lb vibrant, happy cat to only about 6 lbs, weak and falling over when he tries to walk. Our whole family is in agony because we have to make the decision to put our baby Teddy to sleep peacefully before an emergency rupture in his lungs happen! We do NOT want him to suffer and this is the hardest decision I will ever make!

    To think this could have been avoided and he would be fine right now is heartbreaking!

  7. jhofve77
    August 12, 2011 at 10:08 am

    Well, it’s not up to you OR your vet. Rabies vaccination is governed by state and local laws. Your local shelter or the State Veterinarian can advise you on the legal requirements in your area.

  8. Mari
    August 12, 2011 at 8:11 am

    I have a question about giving kittens rabies shots. First my new kitten is (at time of typing) 13 weeks old. I was told by the vet receptionist said that I was to bring my kitten back to the Vet office in 3 or 4 weeks for the booster shot of rabie’s vaccine or the first shot was ONLY a waste of money and time. I am very confused about this. One vet said not to give 1st rabie shot till he was 16 weeks. Another vet said NO he does not have to have a booster until he is almost a year but agreed 12 to 16 weeks of age is good for the first rabies shot. PLease be specific in How often and when is ok give the first and booster shot of rabies. I know he will need a booster ever 3 to ten years and I’m ok with that. but the first and one year booster is Quite confusing.

  9. jhofve77
    January 10, 2011 at 3:22 am

    Sorry, I can’t give individual veterinary advice over the internet. As the article states, Dr. Schultz considers a single distemper vaccine to be effective for life. While adult cats are typically resistant, if they do get distemper, it can be fatal. Please discuss your particular situation with your veterinarian.

  10. George
    January 9, 2011 at 9:02 pm

    I have two adult indoor cats now (10 yrs old and 5 yrs old) and am now in process of adopting a third. We’re adopting him from our local shelter. He’s 2 yrs old, has had all his shots, has tested negative for FIV / FELV and is going to be spayed before we bring him home. I know that my 10 yr. old cat had all of her shots as a kitten. However, I don’t know anything about whether my 5 yr. old acat has ever been vaccinated (We adopted him as a stray two years ago, had him tested for FIV / FELV (negative) and had him spayed).
    I understand that state law governs as far as the rabies vaccine.
    However, I’m wondering whether in this situation I should have my 5 year old vaccinated for feline distemper?

  11. jhofve77
    January 7, 2011 at 10:46 am

    Hi Beth, thanks for letting me know about this. I just spent about 20 minutes on the phone with a supervisor at Merial, and you’re right, they no longer provide that information due to privacy concerns. I’ve suggested that they provide an opt-in referral list on their website for vets who want potential clients to know they use Purevax. Merial does have a function on their site (click here, it’s in the right-hand navigation bar) where you can put in your zip code and it will give you the names of all clinics that use *any* Merial products. However, since most clinics use Frontline and/or Heartgard, you’d still have to call each one to find out if they also use Purevax. At least it will narrow down the list for you.

  12. Beth
    January 3, 2011 at 3:16 pm

    I contacted Merial to find out what vet in my area uses the Purevax rabies vaccine for cats. My vet does not. Merial would not release that information; not helpful at all!!

  13. Mary Ellen
    December 3, 2010 at 3:07 pm

    I recently rescued/adopted a stray cat that I had been feeding for several months. My usual vet was on vacation so I took him to another veterinary practice for neutering and first round of vaccines. I was less than pleased — they were unable to remove him from the carrier and treated him as they would a feral cat – ridiculous because the cat is totally tame and mellow around me. I picked him up the next day, brought him home and placed him in a guest bedroom. The poor cat was sick for nearly 10 days, sneezing, throwing up, lethargic, etc. He received the standard feline panleukopenia–rhinotracheitis (feline herpesvirus)–calicivirus vaccine, the Purevac Rabies (I asked for that) and Feline Leukemia — because he will be going outside in warmer weather — kind of sorry I did that one. He is to be boostered this week. My question is, do I need to booster his shots at all, especially given his very bad reaction. I have two very old cats, one with CRF and I never let them be vaccinated. I would appreciate your advice on this one. BTW this cat is a bobtail and estimated to be between 1 and 3 years old. I had been feeding him for about 8 months before he trusted me enough to let me adopt him.

  14. jhofve77
    November 26, 2010 at 6:42 pm

    We must recommend the rabies vaccine according to whatever the law is in your area; this may vary by city, county and state. In Colorado, the law is that it must follow the directions on the label, and these can also vary. The Merial Purevax is an annual vaccine…but because it is SO much safer than the 3-year killed vaccines, I’d really recommend trying to find a vet who uses it!

  15. Debra Metler
    November 24, 2010 at 9:19 pm

    Hi, I may have missed this in your article but how often do you recommend giving the rabies vaccine to cats. My cat had her last rabies vaccine about 20 months ago and I thought that 3 years between rabies vaccines was adequate (from things I’ve read) but now I’m concerned about this and wondered what you recommend. Thanks, Debbie Metler

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