It’s possible that every body has a mission in life of making a living by securing food, shelter, and a means of reproduction. That includes all living things from the tiniest virus to the backyard dairy goat. It is pretty obvious how the goat goes about this-a human being is coerced into bringing food and water, and providing shelter. It may not be so obvious how this happens at the level of virus and bacteria. These organisms are so tiny, they can’t be seen with the naked eye. But rest assured, they too have the same mission as higher life forms-sometimes at a high cost to people and livestock because they are disease-causing agents. Vaccinations have been created to deal with these agents of destruction.
In recent decades, advancements in antibiotic therapies and the ability to vaccinate have provided an amazing drop in the occurrence of some diseases. These advancements have even wiped out smallpox and lowered the incidence of polio and common infections like strep and staph.
Vaccination against a disease, how that works, and why it sometimes fails applies equally to a human as it would to a goat, or any other mammal.
The causes of disease can be thought of as belonging to two large general groups: Non-living substances (like chemical toxins), and living substances (like the previously mentioned virus and bacteria as well as protozoa, and large parasites like worms and lice). NOTE- nobody is quite sure about where prions belong in that mix!
Fortunately nature has provided for defense against disease. Two types of defense are thought of as being the innate or non-specific response, and the specific response.
Innate or non-specific resistance examples would be the skin acting as a physical barrier, salvia that washes the mouth constantly, mucus in the respiratory tract trapping particles, the cough/sneeze mechanism, and tears that wash the eye. These responses are present at birth and can be influenced by heredity, nutrition, and environment.
Then there is the specific resistance response to disease, which stems from white blood cells in the circulatory system being exposed to the antigenic portion of the disease causing substance. An antigen is any substance capable of causing the production of antibodies and then causing a reaction specifically with those antibodies in a detectable manner. Here is where it gets REALLY interesting! Natural exposure to antigens can occur when disease occurs. Like when a goat has orf (soremouth, contagious ecthyma caused by parapox virus) and then becomes "immune" and never has another orf outbreak. Or exposure can occur artificially by means of inoculation with the infectious agent that has been rendered unable to cause disease, such as when a goat is vaccinated against leptospirosis and doesn’t succumb even when intentionally infected with the bacteria.
The artificial exposure by means of inoculation is called vaccination. Are all vaccinations successful at preventing disease at all times? What makes vaccination a success or a failure? These are questions which have differing answers.
The immune system makes for very complicated and very awe-inspiring study! On a cellular level, each cell is constantly at risk of becoming infected by some opportunistic organism trying to accomplish those "missions" mentioned at the beginning of this article.
In simplistic terms, there are certain specialized cells called "white blood cells" within the circulatory system that respond to invasion by disease causing organisms. When a vaccine is administrated, a substance is introduced into the body that the immune system will recognize as an invader. These white blood cells respond locally, and specifically learn to identify and neutralize that disease-causing organism. The really amazing thing is that the immune system remembers how to make that specific white blood cell. The next time that organism gets into the body the immune system has the ability to quickly call up those pre-existing specialized white blood cells as well as make more upon that "pattern" in order to neutralize that organism. This prevents the invader from having a chance to overwhelm the system.
A lot of people don’t understand that a vaccination does not prevent infection by the organism! The disease-causing organism is present in the body, but the immune system has the white blood cells, which "remember" exactly how to neutralize that specific agent. It’s sort of like getting a warning that an invading army is going to be exactly on a certain location and with exactly those armaments and then special forces are sent in to neutralize that threat.
Many factors influence the success or failure of a vaccine in providing protection from a disease. There are factors associated with the animal, with the vaccine formulation and handling, and environment/management issues. All have an impact upon whether or not the vaccine will protect the animal from disease.
The very young and the very old may have a difficult time mounting a healthy immune response. The very young may not yet have the maturity to have a fully functioning immune system. If the newborn had a fully functioning immune system it would lead to complications while still in the womb. So, Nature got around that by ensuring the immune system matures after birth. The stopgap measure of colostrum being chock full of antibodies ensures the newborn has defense against diseases until that maturation process is completed. Remember, in order for there to be specific antibodies in the dam’s colostrum, she must have first been exposed in a timely manner (either naturally or by vaccination) to the disease. Also the newborn has to get enough of the colostrum in a timely manner to ensure protection. For goat kids it is suggested colostrum be fed a minimum of at least 10% of birth weight in first 12 hours of life to ensure protection.
In early life, the presence of these antibodies can actually interfere with vaccine response for up to two months or longer. Likewise the very old may have deficiencies of immune response due to the body just not having resources to repair itself as quickly as in a younger animal. They are literally just worn out.
Biological variations due to inherited traits can influence vaccination success, too. Even though properly immunized, an animal may not mount a strong response. On a genetic level this is almost always due to some lack of an important factor within the immune system. An extreme example of this phenomenon is the different strains of mice bred for a specific vulnerability to a disease.
Nutrition certainly plays a very important role in how the immune system may respond to any challenge. And, it is not just having enough calories to maintain body condition that is important. Many studies have shown minerals and vitamins are vital to a healthy immune response. Some of the more important are selenium, zinc, copper, and vitamins A, D and E. Also, a fact sometimes overlooked, is the importance of protein levels. The building blocks of protein are amino acids and guess what? Antibodies are made out of amino acids!
If an animal that is already suffering from a disease is vaccinated, the immune system may be overwhelmed and unable to mount a specific response to the vaccination. I always think of the comedy classic of Lucille Ball and the candy factory production line as a way to picture this fact. Throw too much, too fast at the immune system and it may be overwhelmed. It is suggested that at least two weeks should pass after an animal has returned to health before vaccinating. The same recommendation stands for antibiotic therapy, try to wait at least two weeks after the last dose before vaccinating. In a subtler way this is also true of vaccination in the face of an outbreak. Animals are only stressed more and don’t receive any benefit for at least two weeks after vaccination. If the disease is already present then what benefit is gained?
Steroids can interfere with the immune system response, too. One of most commonly given to goats is dexamethasone. The waiting period after a dose is not set, but at least a month is often recommended. But, did you know that when stressed a goat would produce a natural steroid? Animals that are over crowded, undernourished or recently shipped are very vulnerable to having a high level of naturally occurring steroids. That in turn will depress immune response to both vaccination and to actual disease challenge. A vaccine administered at that time of stress, would give less protection.
There are considerations about the vaccine itself being formulated properly. The immune response is very specific and the vaccine might have the wrong serotype of the organism. When vaccinating for a specific serotype (or group of serotype) and a completely different serotype is the disease-causing agent, the protection may be minimal or even nonexistent. This is probably much more a problem with viral caused diseases than bacterial, due to the fact a virus can mutate much faster.
Potency and purity have a lot to do with how effective a particular vaccine may perform. Potency refers to the amount of a particular antigen (that specific part of the disease organism that causes the immune system to respond) within the vaccine. Careful control to ensure each and every dose has the correct amount to cause the immune system to respond it vital
Purity refers to whether or not the vaccine contains any other organisms or mycotoxins. Mycotoxins are by products of the manufacture of the vaccine. And, they areas the name implies, toxic. A real problem of late has been the presence of mycotoxins in vaccines for ruminants. Loss of production has been documented on dairy cow operations as a direct result of mycotoxins being present in vaccines administered to cattle. These impurities are easy to filter out, but it takes time and it does cost the manufacturer more. When present in vaccine mycotoxins cause the animal to run a high fever and be quite ill for a time. They can even depress the immune system for an extended length of time. This can result in not only a lack of proper response to the vaccine but also the animal being vulnerable to other disease and infections!
On a personal note, I have had goats run a 106ºF fever within a few hours of using a vaccine. This can result in founder due to massive die off of rumen bacteria from the fever and result in rumen acidosis. Consult an attending veterinarian about treatment options. I found the symptoms themselves manageable by administering probiotic and banamine or aspirin and monitoring temperature.
However the long term impact of a depression in the immune system function is not itself directly treatable. So what is the answer? Obviously clean up the vaccine! Maybe if every time such a reaction happened, the producer would document that fact and write the vaccine manufacturer directly to complain, someone would get the message. Even if only one manufacturer would respond positively by providing a "cleaner" product, then we could use that product to the exclusion of the "dirty" vaccines.
Of course vaccines for people are the most thoroughly purified. People (or their survivors) sue when they have a bad reaction due to an impurity in a vaccine. That is some pretty potent motivation to the vaccine manufacturers to provide a pure product.
And the horse vaccines are pretty clean, too, due to the fact it could be the backyard pony or a seven million-dollar Triple Crown winner on the receiving end of the needle. The same can be said of the dog/cat vaccines. People are very emotionally attached and will be very loud in their complaints, if their pet suffers from a reaction to an impure vaccine.
A bottle of vaccine should be thought of as a living creature which has a specific and limited lifetime. Using outdated bottles of vaccine is not a good idea. It does no good to use a vaccine that doesn’t elicit as strong an immune response as possible. Outdated vaccines certainly bear that risk. The antigen component of a vaccine can be very fragile and degrade over time. Remember, the antigenic portion of the vaccine is the part that actually makes the immune system respond.
All vaccines have limitations, some more than others. Often a vaccine can provide almost 100 percent guarantee of animal being protected from disease. And, sometimes that percentage is far below 100. Here the point should be brought up that the larger scope of a vaccination program in a population of animals is NOT to prevent the disease totally, but instead to stop it from spreading so quickly and so overwhelmingly, as to wipe out that population. So, even in those cases where vaccination is known to only provide limited protection, it may be enough to prevent an epidemic.
Now here is where human error really enters into the picture for vaccination failures. Things like handling, mixing, and timing of vaccination really impact success. It is imperative that label directions be read and fully understood about storage and handling of vaccines. If a vaccine is mixed before use it should be exactly as the label directs. The vaccine should then be promptly used and not stored mixed.
The vaccine purchase source is very important to ensure that from manufacturer to user, storage and handling has been according to label directions. Once it leaves the manufacturer, temperature during storage and transit is probably the most critical element of insuring that vaccine remains effective. Read the label and follow directions for storage.
When to vaccinate is important, as it takes at least two weeks after vaccination for the animal’s immune system to be fully able to respond to that specific disease challenge. If a vaccine recommends a booster then it will be two weeks after the last booster recommended. Never neglect to give the number and timing of the vaccinations per the label directions. Many times the ability of a vaccine to stimulate a strong immune response is very low and repeated vaccinations are needed to provide adequate protection.
Any vaccinated animal may still be infected if the exposure to the organism is overwhelmingly large. Remember, vaccination doesn’t prevent the disease organism from getting into the body, it only provides pre-patterned white blood cells to neutralize that specific organism.
Missed an animal in the vaccination process can be a problem as well. Maybe one escapes, or the needle goes through both layers of the skin and out the other side to squirt the vaccine all over. Someone might try combining several health tasks at once and forget one. These things are real reasons for vaccine failures and must be managed to prevent. When vaccinating, it is best to concentrate efforts on just the one task to ensure success.
The route of administering a vaccine is very important. The way the vaccine is formulated is very specific to where it will be put in that animal’s body. The immune system has recognized it as "foreign" and process it to make white blood cells that REMEMBER how to neutralize the organism. It is not a good idea to do an intra-muscular (IM) injection with a vaccine labeled sub-Q. The type of adjuvant (a substance that provides a generalized inflammatory immune response) and antigen has been formulated for that specific administration route. And, guess what? Those folks recommending this change don’t have any scientific studies proving that route provides as good (or ANY!) protection as the tested and labeled route.
Another consideration in the practice of administering vaccine is the gauge and length of the needle. Nerves and joints especially can be damaged by failing to consider their proximity to the injection site. If you use too large a gauge of a needle the vaccine may actually leak back outside the animal and not provide any protection. If you were to hit an artery or vein and inject the vaccine, not only would it not provide protection, but might even sicken or kill the animal.
Finally, don’t forget the best practice is to work closely with a veterinarian and always follow his/her instructions when using a vaccine extra label, or the manufacturers label instructions when using vaccine on a labeled species. They are the most knowledgeable about this subject.
Donna R. Myers-Raybon raises purebred and American Nubian dairy goats along with husband David E. Raybon, under the herd name of Safehaven Nubians in eastern Tennessee. She has a Bachelor of Science degree in psychology along with a second major of biology and minor in chemistry. She has successfully completed courses in microbiology, immunology, cellular biology, and biochemistry. She authors this article as an interested lay person and dairy goat producer to the interested layperson and dairy goat producer.