By: Shannon Barton
The Immune System
When the body senses foreign substances, called antigens, the immune system works to recognize and get rid of them. It utilizes white blood cells, or leukocytes, to do this. These typically consist of macrophages, B-lymphocytes, and T-lymphocytes. Macrophages swallow up and digest germs, plus dead or dying cells. They leave behind parts of antigens and the body identifies and stimulates antibodies to attack those pieces. B-lymphocytes are defensive, producing antibodies that attack the antigens left behind by the macrophages. T-lymphocytes, also defensive, attack cells in the body that have already been infected and serve as memory cells. When battling specific illnesses for the first time, the immune system remembers how to conquer it, so it can keep a record of how to defend itself against the same germ in the future.
The Infection Operation
Vaccines work alongside the immune system, guiding it to be able to fight off diseases and infection. Such immunizations work by imitating an infection with weakened or inactive parts of an antigen, spurring T-lymphocytes and antibodies into action. Once the imitated infection is gone, the immune system is left with memory T-lymphocytes and B-lymphocytes that will remember how to fight off that illness. Vaccines, because they introduce the body with an amount of a certain type of antigen, though minimal, may cause minor symptoms within an individual. However, as the body builds its immunity, this is expected.
After a vaccination, it may take several weeks for the body to produce T-lymphocytes and B-lymphocytes, thus not providing immediate protection after a shot. Some vaccines require multiple doses, to allow for the production of long-lived antibodies and the development of memory cells.
Types of Vaccines & Composition
Many varying approaches are made when it comes to developing a vaccine, based upon information about the infections the vaccine will prevent, environmental conditions, geographical factors, and more. Several types of vaccines are used, the main ones being attenuated vaccines, inactivated vaccines, toxoid vaccines, subunit vaccines, and conjugate vaccines.
Live, attenuated vaccines fight viruses and bacteria. These vaccines contain a version of the living virus or bacteria that has been weakened. Such vaccines are good for informing the immune system. Those with weakened immune systems, however, cannot receive live vaccines.
Inactivated vaccines also fight viruses and bacteria. They are made by inactivating a germ during the process of making the vaccine. Often, multiple doses are required for effectiveness.
Toxoid vaccines prevent diseases caused by bacteria that produce toxins in the body. In the process of making these vaccines, the toxins are weakened so they cannot cause illness.
Subunit vaccines include only parts of the virus or bacteria. They contain only the essential antigens rather than all other parts that make up the germ, thus side effects are less common.
Conjugate vaccines fight bacteria that have antigens with an outer coating of polysaccharides, disguising it. Conjugate vaccines are effective for these types of bacteria because they connect the polysaccharides to antigens that the immune system responds to very well. This linkage helps the immature immune system react to the coating and develop an immune response.
Vaccines contain either small fragments of the disease-causing agent or the blueprints for making the tiny fragments. They also contain other ingredients to keep the vaccine safe and effective. Each vaccine is composed of an antigen, preservatives, stabilizers, surfactants, residuals, diluents, and adjuvants.
Each vaccine under development has to have screenings and evaluations to determine which antigen should be used to invoke an immune response. This phase is done without testing on humans, with the experimental vaccine first tested in animals. If the vaccine triggers an immune response, it is then tested in human clinical trials in three different phases. Following the results of the trials, safety for regulatory and public health policy approvals are evaluated.
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