Hermine E. Smikle
The term immunity refers to the stage where an individual if infected by a disease organism will not suffer life threatening consequences. There are three types of immunity.
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Short term immunity: When the disease organism enters the body, the body responds with a huge increase in the production of white blood cells. These white blood cells attack the invading organisms. If the counter attack is successful in destroying the disease carrying organisms, the patient recovers, and the body's defenses are de- mobilized and the white blood cells return to their normal levels.
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In this stage high levels of overall resistance can build up within the human body. If all persons in a community respond in a similar way, then an epidemic will be averted.
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Long Term Immunity: the body's defense system retains a memory of the infection by the diseases organisms. If it returns, the process of immune system counter attack begins again with greater strength.
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Natural Immunity: The immunity for a disease can be passed from parent to offspring across generations. Examples are:
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certain blood types which hinders nourishment for the organism
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chemical constituency within the body's defense system
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The immune system has evolved to deal with an enormous number and varieties of foreign substances. The response is graded to the level of the invasion. The body provides a vigorous response when needed. For example the arrival of a new organism on the skin does not call for a major response, since the normal flora of the skin does not invade the inner cells. Antigens are the proteins in viruses and bacteria that trigger an immune response. A satisfactory immune response gives protection from repeated disease caused by a specific virus or bacteria.
When an invading pathogen enters and replicate in the host, the viral antigen is manufactured. This elicits an immune response by the host. The host's immune system must discriminate between foreign antigens that are not produced by the host and the body's own proteins (i.e. hormones such insulin, and cell proteins that make up muscle)
After an infection by a virus or bacteria, the body's immune system competes with the virus or bacteria that are replicating rapidly, to limit the replication and then to clear them from the body. The host uses a variety of weapons to fight the attack. If, the host's immune system succeeds to defeat the pathogen, then pathogens are destroyed, and the host develops immunity to that virus or bacteria. If the pathogen is not defeated and expelled from the body, then the infection ends with the death of the host, or the host develops a chronic persistent infection.
Vaccination is the medical strategy for stimulating the immune system to protect against a specific disease agent before exposure
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. The provoking an immune response before a natural viral attack, acts as a blueprint immunologic memory, so that cells involved in making the potential anti-viral immune response are primed and alert. When confronted with a full strength infectious virus these primed cells react quickly and with greater intensity than the unprimed cells. The host has the ability to better able to successfully combat and control the infection.
There are many different routes for the development of vaccines. Three strategies are listed below.
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The use of live virus. These are prepared in the laboratory animal and tissue culture. The ability of the virus to cause an infection is reduced. This process is called attenuation. A form of virus is developed with just enough potency to cause an immune response, but not enough to cause a disease.
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The virus is inactivated, that is killed by the use of a chemical. The killed virus is then tested for its capacity to cause an immune response.
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The preparation of a sub-unit, recombinant or DNA vaccine.
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The purpose of vaccines
The purpose of vaccination is to limit the impact of an infectious disease. The only disease that was eliminated by vaccination is the smallpox disease. This was possible because smallpox virus is a strict human pathogen, the only host is man, and it has no animal reservoir. For childhood diseases such as measles, vaccination seeks to protect the community as well as the individual. Vaccination is also used to protect individuals at high risk of acquiring a specific infection, for example people in certain high risk professions.
Vaccination is valuable to the whole community. If the majority of people are vaccinated against an infection, the rest of the population is also protected. This is called the herd immunity principle. Herd Immunity provides protection of the few unvaccinated by the immunity of the bulk of the population.