These refer primarily to dogs, but the information applies to all species including humans.

  References used:
Tizard's Veterinary Immunology textbook.
F & S Newsletter - Vol#1 Number 8  November 1992.

Vaccines are used in both humans and animals to stimulate the immune system to produce antibodies against harmful bacteria and virus. Although sufficient immunity and antibodies are usually generated, this is not 100% and anything less than adequate disease protection is termed a vaccination failure. There are multiple reasons why a vaccine can fail to produce adequate protection and, this will explore some of the possibilities. 

We all have known human individuals and families who seem to have more illnesses than others. In other words, they catch seemingly every flu or cold that passes through. Additionally, they tend to become "sicker" than the average person that contracts the disease. Likewise, there are individuals and families that seem to remain very healthy (the never-miss-a-day-of-work-or-school type) even when the seasonal colds and flu’s take their toll. In reality, no two individuals have the same immune systems.  Some have very good ones and some very weak. Some people have sensitive immune systems (allergies) and some do not. The point here is that all immune systems are not the same and each individual will respond differently to a disease or vaccine. Consequently, there are some individuals that probably never need a vaccination and some that need a few and then there are individuals (with weak immune systems) that no matter how often they are vaccinated, complete protection will never be achieved.  Up to this point, this has been about people but animals are no exception.  Each individual immune system is different, therefore, with different capabilities of responding to a vaccine. Take a litter of ten puppies, statistically there are probably two that would never need a vaccine and have such great immune systems that even parvovirus would not be detrimental to their health. There are about 6 more that need a series of 3 or 4 vaccines to stimulate their immune systems to a level of achieving protection. At the worst end, are 2 more puppies that no matter how often they are vaccinated, they will never have complete protection.  This above phenomenon explains why when parvovirus strikes a litter, it traditionally does not kill them all, and in fact, some may never appear ill while others will die. Since we do not know who has the good, average, or bad immune systems, we vaccinate each animal as if its immune system was poor. This is the safest way to assure at least average disease protection. 

This next little bit refers to dogs, as usual there is nothing to be found in this area pertaining to goats specifically, but is very informative and a good example:
A second factor determining the immune responses in dogs are the breeds themselves. Some breeds of dogs (and certain lines within every species) just don't respond well to vaccines, in the canine this is especially true of parvovirus. The most notable immune deficient breed are the Rottweilers as well as Akitas and Shar-Peis. No matter how often one vaccinates these individuals against parvovirus, a certain percentage will not have adequate parvovirus protection. This is not a problem with the vaccines but it is with genetics itself.
 Actually, this should be no medical surprise, as humans are no exception. African Americans are more susceptible to sickle cell anemia than is the Caucasian population. Likewise, the white population is more susceptible to breast cancer and certain skin tumors. Genetics play a role in humans and in animals. Within every species are individual genetic lines that differ. There are some individuals is every species that cannot genetically respond adequately to vaccines. 

Concurrent medications that are being given can affect their ability to respond to a vaccine. Steroids given at over 1 milligram per pound of body weight can be immunosuppressive and this individual may not respond well to a vaccine. 

Improper usage of the vaccines can greatly affect the response to them. We've all heard of instances where a veterinarian or breeder will suggest that a small or young individual should not receive a full dose of a vaccine. This is absolutely false and has no scientific basis. If you administer 1/2 the normal vaccine dose to a small or young animal then expect little, if any, protective immunity. Please, please do not let anyone teach you otherwise as you will be placing you animal at great risk. This "1/2 dose" theory is wrong and those that adhere to it are wrong. Many things are negotiable but this is not. 

The next time you hear someone say "the vaccines were no good" or "the vaccines killed my animal", please understand what really happened. All immune systems are not equal and each respond differently to immunizations. Was the vaccine really no good or did genetics prevent the individual from responding to the vaccine? In young animals were they due to age not completely protected, and developed the disease anyway? 

This is not to imply that all vaccines are perfect as surely they are not. Only medical research can improve them but only genetics can control the immune response that they can stimulate. 

Most "vaccine failures" are truly due to age and genetic failures, and, therefore, even the best vaccines of tomorrow will never achieve 100% protection in every individual. It has always been said that medicine is not an exact science and here is proof to back that statement up.

For more information see Vaccines and Vaccine Faillure, Why Vaccines Don't Always Work by Julie Funk College of Veterinary Medicine North Carolina State University Raleigh, NC

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  References used:
Tizard's Veterinary Immunology textbook.
F & S Newsletter - Vol#1 Number 8  November 1992.

There are many myths as to how rapidly a vaccine can work. 

This area is well defined in the Tizard's Veterinary Immunology textbook. Here are the facts. When an animal is vaccinated for the first time, it will have very little immunity until about ten days post vaccination. It is at this time that the body has produced antibodies at a high enough level to provide at least some immunity.  Full immunity will not be received until the patient receives its 2nd vaccine (booster) which is usually administered two to three weeks after the first vaccine.  In fact, full immunity will not be accomplished until seven days after the second booster. 

Now, what all this means is that, an animal does not have total protective immunity until one week after the second booster is administered. This is the same for most vaccines and all species of animal, including humans. An exception is Rabies where one vaccine appears to be sufficient. 

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