Stimulate Immunity

Vaccines are manufactured biological preparations. When administered to cattle a vaccine can fool the body's immune system into believing it is encountering the actual disease. In this way a calf's immune system is stimulated to build an immunity against a particular disease organism. To fool the body without actually causing the disease, the vaccine preparation must be either killed or attenuated. Attenuated means the vaccine organism is modified so it no longer causes disease.

Killed and modified live vaccines are the most common types of vaccines. Killed vaccines are made by growing the virus or bacteria, then inactivating or killing the organisms using either heat or chemical.

In killed vaccines an adjuvant is added to the solution of killed organisms to help it stimulate the immune system. Dead virus or bacteria are not as easily recognized by the immune system without an adjuvant. The adjuvant also holds the killed organisms at the injection site. This allows time for the immune cells to respond to it.

Modified live vaccines are made from an isolate of virus or bacteria. The virus has been attenuated. Attenuated means the virus cannot cause disease but it can reproduce in the body cells and stimulate immunity.

A modified live organism is grown in a production facility, then it is dried to a cake in the vaccine bottle. This process is necessary because most modified live organisms are not stable when left in solution. To use modified live vaccines a liquid must be mixed with the modified live cake to reconstitute it. It is best to mix the vaccine a short time before use. The reconstituting liquid can be sterile water or a killed liquid vaccine. In either case, the liquid mixed should be approved for use with the modified live fraction.

Killed vaccines may be killed viruses, killed bacteria called bacterins, or killed toxins called toxoids. Modified live vaccines are usually called MLV for modified live virus or avirulent bacteria.

All vaccines approved by USDA undergo significant testing to prove efficacy, safety, and sterility. These tests are conducted in susceptible animals capable of developing immunity following vaccination. If animals are not susceptible because of poor nutrition, incubating of an organism, or the presence of maternal antibody, then vaccination with a proven tested vaccine may not provide protection.

Vaccines are tested for sterility before they are released for sale. Once a bottle seal is broken, a needle inserted into the bottle, and the product is exposed to air and possible bacteria, sterility is no longer assured. Make an effort to maintain sterility of the vaccine by inserting new, sterile needles. Fill syringes with a new sterile needle and use a different needle to vaccinate.

Vaccines generally must be stored in cooler temperatures to maintain potency. While working cattle keep the vaccine cool, out of sunlight, and mix only enough modified life vaccine to work a few head.