Vaccines and Immunization
- 06-24-2003, 01:38 AM
Vaccines and Immunization
This is written on pg 41-45 in the Simon and Schuster Encyclopedia of Health, Medicine, and body: (typing this up)
The basis of all vaccination is the antigen-antibody reaction. Antigens are substances that induce formation of antibodies, the latter being protective protein substances produced by the organism in response to the presence of "foreign" substances (antigens), often of bacterial or viral origin. An antibody combines with the antigen that provoked its formation and renders it harmless. Once an antibody has been produced in response to the antigen of a particular disease, the organism can produce it very quickly in a response to a subsequent attack of the same disase; this is known as (acquired) immunity to the antigen. Antigens are usually proteins, but some fats and polysaccharides may also have antigenic properties. Antibodies are produced in the cells or occur as plasma proteins belonging to the so-called gamma globulins. Inoculation (active immunization) consists in introducing certain antigens into the organism in order to provoke the formation of defensive antibodies, ie, it is a deliberate infection with a disease in a mild form in order to confer immunity against a subsequent attack of that disease. Repeated inoculation can thus induce the formation of a relatively large quantity of the antibody. The immunity obtained in this way may remain effective or years and can be restored again and again by booster injections. The drawback of active immunization is that it takes a relatively long time for the immunity to develop, so that it may be too slow-acting in acute cases of disease.
With active immunization a distinction is to be drawn among inoculation with live microbes, with dead microbes, and with toxoids. Live microbes used for the purpose are so modified as to be practically harmless , yet still capable of conferring immunity. Dead microbes for inoculation have been killed in ways taht likewise preserve their immunity-inducing properties. Toxoids are toxins that have been so treated as to destroy their toxicity, but leave them still able to induce the formation of antibodies. The term VACCINATION is sometimes more specifically used to denote the injection of live microbes (attenuated strains of microbes tha have lost their virulence). Such vaccines are used against smallpox. For immunization against tuberculosis, live bacteria of bovine tuberculosis are used, which do not produce the disease in man; this treatment must not, however, be given to persons who have already had tuberculosis. Dead microbes are used for immunization against measles, poliomylelitis, influenza, rabies, whooping cough, typhoid and cholera. Toxoids are used for conferring immunity against diphtheria and tetanus.
In addition to the classification by immunization with live microbes, dead microbes and toxoids, a distinction can be drawn between vaccines that contain only the antigen in a fluid medium, eg a phusiological salt solution, and vaccines in which the antigen adheres to the surface of an adsorbent substance, usually aluminum oxide, so that the antigen enters the bloodstream gradually and the production of antibody is correspondingly increased.
With PASSIVE IMMUNIZATION the patient is injected with a serum containing "ready-made" antibodies of animal or human origin--instead of the body having to produce them itself. The advantage of this method is that the treatment acts quickly;its disadvantage is that the immunitiy is of short duration (only 8-14 days with animal sera). Passsive immunization is therefore appropriate only in cases where the time between infection and the anticipated outbreak of the disease is too short to enable the body to build up its own defenses. In most cases a combination of passive and active immunization is applied, in order to obtain a more lasting as well as immediate protection.
SERA for passive immunization are obtained mostly from horses, cows, sheep, or pigs. The animal is treated with the antigen of a particular disease until it produces a sufficient amount of antibody. Blood is then taken from the animal and suitable prepared (EXBANANA NOTE: Seems odd). Untreated blood serum from such an animal is called a NATIVE serum. Because of their high overall content of foreign proteins native sera are not easily tollerated by the human patient and are not normally employed for immunization. By separating out these proteins and breaking down, by enzyme action, the serum globulin with which the antibodies are associated, a serum is obtained which produces much less of the undesirable and possibly dangerous reaction in the patient to the animal protein and which nevertheless achieves effective immunization. But even with such an improved serum it is always necessary first to test the patient's reaction to it by giving a trial injection. In order to reduce the risk of allergic reactions (due to the formation of antibodies against foreign proteins which are not in themselves harmful) when repeated doses of the same serum are given, the rule is first to administer horse serum, then cow serum, and finally sheep serum. Serum treatment is now available for a number of disases including diphtheria, tetanus, anthrax, meat poisoning, and snakebite.
Part II in a sec
- 06-24-2003, 02:06 AM
In recent years, besides animal sera, human sera containing antibodies have been used for passive immunization in the form of gamma globulin or hyperimmunoglobulin. Gamma globulin is that fraction of the globulin in the blood with which most of the immune antibodies are associated. Immunoglobins are proteins that are capable of acting as antibodies. Hyperimmunoglobulins are associated with specific antibodies to whooping cough, teanus, mumps, measles, and smallpox. By and large, human antibodies have one major advantage over animal antibodies: the patient's defensive mechanism does not respond to them as to foreign proteins, ie they do not provoke the production of the human patient's own antibodies to the injected antibodies (which in this particular respect act as antigens), as does occur when the altter are of animal origin. Hence there are no undesirable and potentially dangerous allergic defence reactions.
For greater convenience of immunization against several diseases at once, combined vaccines have been produced which contain antigens of three, four, or five diseases. Of course, it must be ensured that the various antigens do not adversely affect one another.
There still exists divergence of opinion on when, and how often, immunization should be applied/ Some experts consider than an infant should be vaccinated against tuberculosis (indeed, as its first vaccination) in the first week of its life. Then, from the third month onward, combined vaccination against diphtheria, whooping cough and teanus can be given three times, at one-monthly intervals. After the eighth month comes the first vaccination against smallpox. When the child is 2 years old, vaccination against diphtheria, whooping cough, and tetanus is repeated, and two doses of oral poliomyelitis vaccine are given. At the age of 6 the child recieves further booster doses of diphtheria and teanus vaccine. If no vaccination against tuberculosis has already been given and if the child has not by then acquired a natural resistance to the disease, TB vaccination should be done now, ie when 6 years old. The second smallpox vaccination is given at the age of 12. Finally, a third booster dose against diphtheria and teanus may be given between the ages of 12 and 14 (with subsequent repitition at three-yearly intervals.
In Germany, as in some other countries, the only immunization required by law is vaccination against smallpox (variola). Every child must be vaccinated in the calenderyear following the years of its birth. A booster injection is required at the age of 12. The most serious complication tha tmay arise in connection with smallpox vaccination is meningitis, which though rare, is more liable to occur as the person grows older. To rule out this complication with certainty, older persons are vaccinated with killed smallpox virus. (exbanana note: Meningitis vaccines are easy to pick up, I got one from cosco)
Poliomyelitis can be caused by three types of virus, and full protection requires vaccination against all of them. In the Salk vaccine the killed virus of all three types is administered in three doses spaced at monthly intervals. In the Sabin oral vaccine the attenuated live virus is given, but not all three types simultaneously: first type I is given, followed by types II and III six to eight weeks later.
The antigen injected against tetamus (lockjaw) is a toxoid-- a bactrerial toxin attenuated by treatment with formaldehyde and adsorbed on aluminum oxide. As untreated tetanus is often fatal and the possibilities of infection are numerous, vaccination against this disease is very important. In the absense of vaccination, temporary (passive) immunity against tetanus after a wound can be given with an injection of antitoxin
- 06-24-2003, 05:29 AM
Thank you EBE- Took some work to type this out and you didnt waste your time..... interesting material....
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