In the last 50 years, vaccinations have made a vast difference in preventing many severe diseases in both humans and their pets. But there is no vaccine in the world that is both 100% effective and 100% safe. A tiny percentage of patients-both human and animal-fail to be protected or have various types of vaccine reactions, but the benefits have outweighed the risks by far. Vaccines have also been blamed for many things without any evidence that the accusation has any truth in it. (For example, some have accused human vaccines of causing autism in children, but studies have found there is no connection.) Humans are vaccinated against many more diseases than animals, and those diseases affect a maximum of 0.2% of the human population. Animals are only vaccinated against diseases that are far more common. Most vaccine reactions are mild-feeling a bit achy and tired for a day or two, pain or swelling at the site of injection, or perhaps running a brief fever. But they can be worse.

In 1991 it was noticed that a certain type of cancer called a fibrosarcoma seemed to occasionally occur in cats at the locations where vaccines had been injected. (This cancer also occurs in humans and animals unrelated to vaccines.) Soon after this discovery, veterinarians began giving cat vaccines in different areas of the body to help researchers figure out what was happening.

The phenomenon became known as Vaccine-Associated Sarcoma, or VAS, and was further studied. The research has shown that the problem is rare but does exist, and that any injection of anything can be related to this cancer, but it occurred most often at sites of leukemia vaccine, and secondly at sites of rabies vaccine. Various studies showed it to happen in-at worst, 3 out of every 10,000 cats vaccinated (0.03%) and-at best, 1 out of every 30,000 cats vaccinated (0.003%). A part of the vaccine called the adjuvant-which helps vaccines be effective-was at first thought to be the cause. It was also found that some cats have a genetic tendency to react this way to vaccines. Other potential causes were thought to be the inflammation of the normal immune response at the injection site, or possibly from debris in the vaccine from the tissue cultures that are used to make vaccines.
Veterinarians strive to follow the rule, "First, do no harm." We want to protect our patients, not harm them. Cats that go outdoors or have contact with outdoor cats (such as hissing through a screen door) have a much larger chance of getting the lethal disease Feline Leukemia (> 10%) than of having a reaction to the vaccine (0.003-0.03%) and should have the vaccine to protect them. But we do not recommend Leukemia vaccinations for cats that are strictly indoors and at low risk of exposure to the disease. However, Rabies vaccine is required by law even for indoor cats (bats get into houses and caught by cats fairly often), so rabies vaccine can be crucial to the life of not only your pet but also yourself. We follow the law on rabies vaccine-and we do feel the law agrees very well with medical reality for this disease.

This issue brought up many questions, discussions, and hot debates among veterinarians and researchers. We've been watching these discussions closely and would like to address some common questions and give what answers we can.
Why do human vaccines last a lifetime but pet vaccines get done yearly? (After all, they've really improved a lot in the last 20 years!) Not all human vaccines last a lifetime-babies and children get frequent boosters, adult flu shots are yearly, and tetanus is every 5-10 years. If you get injured and don't recall when your last tetanus shot was, one will be given. The longevity of protection can depend on which disease or which type of animal it is-dog, cat, and human immune systems are not the same as each other. Pets also have shorter lives, aging faster. Each of the first two years of a dog or cat's life is like 12 of ours, and later years are each like 4-7 of ours. Also, vaccines for pets are labeled "annual" by the manufacturers, and if a veterinarian uses them some other way, s/he must have good reasons why that is acceptable and adequate.

Are any other problems caused by vaccines? Some immune disorders, like Auto Immune Hemolytic Anemia (AIHA) in dogs, were suspected of being related to vaccines, since AIHA can occur from any immune stimulation. Studies to check on this accusation found that 26% of AIHA cases occurred in the month after vaccines, and 74% of them occurred in the other months. If AIHA was not related to vaccines, only 8-10% should occur in the month after vaccines, therefore 16-18% of cases ARE related, but the majority are not. Another accusation is that the reason allergies, cancers, kidney disease, diabetes, thyroid problems, arthritis, and behavioral problems in animals have become more common in recent years might be animals' immune systems being over-stimulated by too many vaccines. Although we vaccinate pets for fewer things than humans, could these problems be related to vaccines? (Many other potential culprits are also being accused of causing these, such as commercial foods, colorings, preservatives, environmental chemicals, new viruses, lifestyle changes, and stress, to name but a few!) No one really knows the answers, but common sense says it would be best not to blast an immune system with too many things at once. Young animals rarely have problems with these things and are very susceptible to serious illnesses, so changes are not recommended there, but it is thought that in later years it may be better to decrease the number of vaccines at one time.

What can we do to stop VAS and vaccine reactions and still protect our patients? A number of ideas have been proposed, although none is 100% perfect. Some feel the problems are not common enough or proven enough to warrant changing. But here are some of the ideas:
--Can we make an effective cat vaccine without adjuvants? A good idea, and a vaccine manufacturer quickly set out to do this. The non-adjuvanted vaccines have been available for a few years, but early reports show they still can cause VAS. In fact, any injection-not even vaccine-can also cause it, although vaccines are the most common.
--Can we make an effective cat vaccine that gets sprayed into the nose like the dog Bordetella vaccine? If so, will that prevent the problem or will they get nasal cancers?
New cat vaccines are available now that are given this way, but to be effective they must be dripped into both eyes and both nostrils. Cats don't tolerate that sort of thing very well, so we do not carry this form of vaccine. It is too early to see if cancers develop in those areas-the vaccine hasn't been on the market long enough to see if such things result. One advantage of the locations used for routine vaccines is that we now do the Leukemia and Rabies vaccines in the hind legs-in the rare case of VAS occurring, we have the option of amputating the leg to save the cat's life. Vaccines given over the shoulders do not give as much chance of successful cure, and those in the nasal passages would be particularly inaccessible for surgical options.
-- Can't we just give vaccines less often? How long do vaccines really last in animals? This is a very complex subject and the focus of much discussion and debate in veterinary circles. There are two kinds of immune protection: Cell Mediated Immunity (CMI) and antibody production. The level of antibodies an animal makes against a certain disease can be measured by a titer test, and some doctors and authorities recommend such testing. But the test is of questionable value. If the titer is high, it suggests-but does not prove-adequate protection from the disease. An animal may have lots of antibodies but no CMI and not really be protected. Yet some animals can be vaccinated multiple times and continue to have an antibody titer of zero! This does not mean they are unprotected from the disease, for they may have developed their protection through very good CMI. There is no way to test CMI protection except by "challenge testing"-trying to give the animal the disease and see if they come down with it-not exactly something you'd want to try on your pet!

Manufacturers label vaccines good for 1 year and they stand behind that quite well. But there are reasons why there have been no accurate studies for how long vaccines actually do last. Thanks to animal rights activists, laws require animal research to be done only on specially bred-for-research laboratory animals whose immune systems aren't exposed to the same things household pets are, so the research may not truly represent real life. In challenge studies to try to give diseases to animals vaccinated only long ago, these animals don't get sick-but neither do the test animals that have NEVER had a vaccine, because their immune systems are not normal-so the test is not valid. It does not prove that the vaccine protected the vaccinated ones if you cannot even give the disease to the unvaccinated ones! We may never be able to prove length of protection using only laboratory animals, yet who would want this research done on their pet?

Since the titer test costs more than re-vaccinating and doesn't prove anything for absolutely sure, in the past it was thought best to simply give the vaccine yearly. It was understood that if the pet already had good enough immunity to the disease, the old vaccine's protection would simply inactivate the new vaccine and no harm was done. But if the immunity level was fading, the new vaccine would stimulate the immune system to trigger better immunity. (The same logic is used when they give a human a tetanus vaccine because they cannot remember when they last got one.) The vast majority of animals had no problem with unneeded vaccines, but a high risk of disease if not vaccinated enough, so it seemed better to protect them and give the vaccines yearly. But over the years, vaccines have been improved so much they are now extremely effective and last longer. We just cannot accurately test how much longer!
One concern is that vaccinating less may give a high risk of problems with something called "Herd Immunity." This is the fact that when most animals have good immunity to a disease, and one that doesn't have good immunity gets the disease, the disease has a hard time spreading. But if the immunity level of the general population is low, even though most have a little bit of immune protection, the disease can find a few whose protection is low enough that the disease can overwhelm it, and they get sick and produce a lot more virus, which may then be able to overwhelm the protection of more animals, and an epidemic gets started. Many veterinarians fear that if we vaccinate less, we will return to the days of epidemics and the deaths of many pets. Still others believe that animals only really need their puppy and kitten series and the one year later boosters and they are protected for life! Thus you will find veterinarians with a variety of opinions on this issue, all believing they are right. The truth is that, as yet, nobody truly knows, but most experts are endorsing a cautious decrease in frequency of the core vaccines.

It has been difficult for veterinarians to advise people on this, because so much is still unknown. If veterinarians use a medical product in a different way than is stated on the product's label, they can be liable for malpractice, even if in their professional judgment, a patient needs the drug used a different way. But veterinarians can use products "off-label" if it is an accepted standard of veterinary medical practice to use the product in such a way. For example, it is technically illegal for a veterinarian to prescribe insulin for a diabetic dog, because that is not on the label. It would cost the manufacturer too much to get approval to put usage in dogs on their label, so they don't bother. But we know insulin works for diabetes in dogs and it is widely used among veterinarians that way, and so when we use it in a medically responsible manner for that purpose, we cannot be found guilty of malpractice for doing so. This has not been the case for vaccines until now-finally the veterinary schools and some veterinary organizations have advocated longer vaccine intervals even though the manufacturers won't. Veterinarians have been caught in the middle for years and you will still find a variety of opinions among different veterinarians.

Please note that we at Broadway Veterinary Clinic. P.C. have been following these issues very closely and are confident that our new recommendations will protect your pet and also decrease the chances of vaccine-related problems. We promise to continue monitoring these issues and stay informed of further developments to keep our recommendations up to date and in the best interest of you and your pet. Although we are adopting the recommendations in this information sheet, it is important to discuss vaccine needs based on evaluation of the individual patient. We are happy to answer your questions and work with you as to the best protection for your pet.

Any change, of course, may have occasional glitches during transition. We anticipate that our computer-generated reminders for vaccine boosters may not be fully accurate right away. We apologize for any inconvenience this may cause. We recommend that when you receive a reminder postcard saying your pet is due for annual examination and vaccine, that you schedule an appointment and plan that it will include a physical examination and a discussion of your pet's individual vaccination needs, with vaccines given or not given as decided at that time. Please note that-as always-dispensing or approving medications for your pet (such as flea and heartworm medications) can only be legally done if there is a valid Doctor-Client-Patient Relationship through our practice, which requires, at the very least, an annual examination.

3/18/07