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Vaccines: The Facts and the Misconceptions


Vaccines have become controversial, whether for people, dogs, cats or other animals; both sides of this debate are passionate to a fault. Many of us remember the horrible parvovirus outbreaks of the 1980’s, but also have concerns about the increasing numbers of auto-immune dieases. Some veterinarians (especially some large corporate hospital chains) vehemently believe every animal should be vaccinated for every disease every year. Other “naturalists” believe that all vaccines are unnecessary and toxic, causing more harm then good. Both extremes play a little loose with the facts.


Vaccines work by giving the immune system “practice” against bacteria or viruses. This practice gives the immune system a head start fighting pathogens, such as viruses and bacteria, which would otherwise normally quickly overwhelm the body’s defenses. Vaccines therefore do nothing to defend against disease on their own, but only assist an individual’s own immune system.


Misconception #1: All vaccines are necessary every year.

Nearly every university study has shown that the vaccines for canine parvovirus, distemper, hepatitis last for longer than a year. While there are vaccines specifically labeled for a 3 year duration, most of the “one year” vaccines for these diseases last longer than their label. Vaccine manufactures are not legally allowed to change their label without resubmitting the vaccine to the FDA, which requires a large amount of time, money and effort.


Misconception #2: Most puppy vaccines provide a lifetime of immunity

This argument usually stems from the vaccines that some children receive, which are not boostered as adults. While this may be true for some viruses, such as coronavirus in puppies,  it is a specifically disease dependent quality. Some vaccines in humans, such as tetanus and rabies, have to be regularly boostered in human adults. With parvovirus for example, there have been many reported cases of dogs who were vaccinated properly as puppies, then skipped vaccines as they aged, only to catch clinical parvovirus.


In the 1990’s in Finland, it was assumed that the distemper vaccine commonly used would have a 5 to 7 year duration, and this protocol was adopted nearly country-wide. Since there had been no cases of distemper in Finland for a decade, this was believed to be risk free. In 1994, an outbreak did occur, and nearly 5000 dogs became sick, with thousands of deaths. Many of the affected dogs had been previously vaccinated as puppies. [1] Immunologists state that the “herd immunity” of the dogs of Finland had finally been reduced to a level where an outbreak could occur.


Misconception #3: As long as your dog stays away from other dogs, there is no need for vaccines.

Unfortunately, the viruses which cause distemper and parvo are very hardy, and can last longer than 6 to 9 months in the environment. This means that if an owner goes someplace where there was a sick dog 6 months ago, they can bring the virus home on their shoes or hands.


Other diseases, such as bordetella, require close dog to dog contact. There is no risk if a dog is isolated from other dogs.

 Misconception #4: Vaccines are completely harmless.

Vaccines stimulate the immune system, which is how they provide immunity. If the system is overstimulated, reactions can occur. These reactions can include facial swelling, hives and local pain. Vaccines have also been implicated as a contributing cause of autoimmune diseases, when the dog’s own immune system begins to attack its own body. Autoimmune diseases can affect any organ, and be potentially fatal. While vaccines may increase the risk of these diseases, they are not the only cause; there are genetic and environmental components as well. Some dogs are genetically predisposed to autoimmune disease, in which case vaccines, foods, allergies, supplements, infections, or anything in the environment has the potential to be a predisposing cause.


Misconception #5: A healthy dog will have no need for vaccines.

This concept is based on the “wild canine resistance” theory, that wild populations of dogs have some innate resistance to these viruses. This immunity is genetic; a known genetic resistance or lack thereof has been documented among dog breeds, such as the susceptibility of Rottweilers to parvovirus. Unfortunately, this resistance is purely genetic, and not related to a more natural environment, raw food or other external factors. Wolf packs have an increased resistance to these diseases because those individuals which are more susceptible die off before they have a chance to produce offspring. Most people would not tolerate this with their personal pets.


Misconception #6: All diseases are present through the entire country.

Many diseases have different prevalence rates in different parts of the country. Leptospirosis is common in Florida and Hawaii, and less prevalent in northern climates. Lyme disease is common in the northeast, and more rare in Florida.


Misconception #7: Measuring titers are a great alternative to vaccination.

Titers measure the level of antibodies to certain diseases, and in some cases this can be a relative measure of the remaining immunity. For some diseases, antibodies are not the primary means of defense, but rather cellular or humoral immunity. This is the ability of the white blood cells to recognize the virus, and is a very difficult thing to measure. This means that some dogs with low antibody titers will have significant resistance, and some dogs with high titers will still be susceptible.


Misconception #8: Rabies, Distemper and Parvovirus have been eradicated, so there is no more risk.

While “Canine Rabies” has been eradicated from the U.S., dogs can unfortunately catch other forms of the virus from other animals[2]. There are many different “species” of the rabies virus, which are all incurable and fatal. Distemper and Parvovirus are still very common in a vast majority of communities.

 Misconception #9: All vaccines are equally efficacious and safe.

Vaccine technology has progressed significantly over the years. In the past, vaccines worked by mixing killed viruses or bacteria with adjuvants (immune stimulants) or used live viruses which had been attenuated (made weaker so as not to cause disease.) Newer vaccines use small pieces of the outside surface of viruses or bacteria (subunits), or organisms which have been genetically modified (modified live) so as not to cause disease. These modified live vaccines tend to be “more gentle” on the immune system, since they don’t stimulate the entire immune system. The subunit vaccines tend to be less reactive, but may not cross-protect if the organism changes or has different forms (as has happened with parvovirus, or with the large number of leptospirosis species.) For some diseases, the newer style of vaccines may not be available at all; each disease causing organism is different.


Misconception #10: Vaccines guarantee against disease.

Since vaccines rely on an individual’s immune system, there is always a chance of vaccine failure. Underlying disease, immuno-suppressive drugs (such as cortisones or prednisone) all have the potential to weaken the immune system, and allow disease to take hold despite vaccination. Some dogs also lack the ability to react to the vaccine at all; there have been reported lines of Rottweilers who never develop an immunity to parvovirus no matter how many vaccines are given.


Misconception #11: The fact that some dogs are never vaccinated and survive proves that they are unnecessary.

Natural immunity to disease does occur in some individuals; if only this was predictable, who specifically needs vaccinating could be precisely determined. Unfortunately, since this is not predictable, who needs vaccines and who does not cannot be determined until it is too late.

 Facts we do know.

Used judiciously, the benefits of disease protection outweigh the risk of side effects.


The American Animal Hospital Association came out with a consensus report on vaccine recommendations. They recommended that dogs be vaccinated with the core vaccines (distemper virus, parvovirus and canine hepatitis) as puppies, at one year of age, then every three years, since this is the proven duration of immunity so far. Other vaccines should be given yearly based on your local disease prevalence and your dogs lifestyle. For example, dogs exposed to other dogs would be vaccinated for bordetella (kennel cough) or vaccinated for leptospirosis in endemic areas. This means that which vaccines will be given, and how often, should be a discussion between a pet owner and a veterinarian, tailored to each individual pet, taking into account the risks present in their community.


I think that vaccines should be viewed the same way as seat-belts. You don’t need your seat-belt a vast majority of the time while driving, but unfortunately at which moment you will need your seat-belt is not known until it is too late. Seat belts also have risks; in some accidents involving fire or water, there is a chance that a seat-belt could trap you in the car and cause your death. But statistically, since when and what type of accident will occur is unknown, the odds are in your favor if you wear your seatbelt when driving. The seatbelt, like vaccines, has a much greater chance of saving you than causing harm. Like any tool, if used properly, vaccines are a valuable resource in giving your pet the longest and happiest life possible.