Immunization

Immunization, the practice of inducing immunity (especially to infection) in a person or animal. This is usually achieved by vaccination, in which a vaccine (a preparation containing antigens) is used to stimulate the production of antibodies and therefore induce active immunity. The vaccine is usually administered by injection, and generally contains either live but attenuated organisms (reduced in virulence), or dead organisms which retain their ability to stimulate antibody production.

Active immunity lasts many years. Passive immunity is induced by the administration of antibodies against a particular infection (passive immunization). Antibodies collected from humans are called immunoglobulins, and those from animals, antisera. Passive immunity lasts for only a few weeks. The earliest form of immunization was variolation, a type of inoculation against smallpox in which part of a scab from a smallpox sufferer was introduced into a scratch on the recipient’s skin.

The practice, developed in about the 5th century AD in India, was potentially very dangerous, since it involved the live smallpox virus, but it greatly reduced overall mortality from the disease. Variolation was not known in Europe until 1721, when Mary Montagu, the wife of the British ambassador to the Ottoman Empire, introduced it from Turkey. In 1796 Jenner successfully protected an 8-year-old boy from smallpox by inoculating him with the related but much less dangerous cowpox virus. In 1885 Pasteur adopted Jenner’s principles to find a vaccine against rabies.

Vaccines have subsequently been produced for other diseases and non-infectious agents, including diphtheria (by the German immunologist Emil von Behring in 1889) and snake venom (by Ehrlich in 1889). In 1890 von Behring and Kitasato first showed that immunity was due to antibodies that appeared in the blood a few days after immunization. In the richer countries of the world, mass immunization of children against major childhood diseases has been successful in reducing morbidity and mortality rates.

In 1974 when the World Health Organization launched the Expanded Programme on Immunization, fewer than 5 per cent of children in developing countries were immunized. By 1991 four-fifths of the world’s children were protected by immunization against diphtheria, whooping cough, tetanus, measles, polio, and tuberculosis, and WHO estimated that 2 million lives were being saved each year. None the less, there is still a heavy toll in preventable disease, with more than a million cases of measles, which is often fatal to malnourished children, for example.

New goals for the 1990s are to eradicate neonatal tetanus and polio and to reduce measles by 90 per cent. WHO’s global eradication of smallpox in 1977 through systematic immunization, and through tracking down the last carriers for treatment, has set a dramatic and encouraging precedent. 1immunity, the ability of an organism to resist infection by means of the immune system. The immune system has two main parts: white blood cells, and antibodies circulating in the bloodstream. Antibodies are proteins produced by B-lymphocytes (a type of white blood cell) in response to exposure to antigens (antibody generators).

Antigens can be micro-organisms, blood from transfusions, cells in transplanted tissues, and any other material not recognized as belonging to the body such as those that cause allergy. Antibodies are dormant until they attach to the specific antigens against which they are effective. They then become activated, and may directly destroy the antigen or ‘label’ it so that a white blood cell can engulf and destroy it. After the body has been exposed to an antigen, ‘memory’ ensures that a later exposure causes antibodies to be produced more quickly and in larger amounts than on the first occasion.

This can produce immunity to a harmful antigen such as a virus, since it is eliminated before it has time to act. In addition, immunity also detects and eliminates the body’s own abnormal cells and denatured proteins, which is a self-monitoring function called immunosurveillance. Cell-mediated immunity is the most reactive part of the immune system, and leads to the production of specific white blood cells (T-cells) in response to antigens. Humoral immunity, the second component, is responsible for the production of specific antibodies to the antigen.

The components may act alone or in combination depending on the situation. Immunity may be induced by artificial means (see immunization). (See also immunology. ) 2Ehrlich, Paul (1854-1915), German physician who founded chemotherapy and made important contributions to bacteriology, haematology, and immunology. As a student, he became interested in aniline dyes, using them for the first time to stain bacteria. He also employed a similar technique to identify the different types of white blood corpuscles and the corresponding leukaemias.

From 1889, he investigated the principles of immunization and two years later devised a means of standardizing diphtheria toxin. In 1911 he introduced the arsenical drug arsphenamine as a treatment for syphilis. He shared the 1908 Nobel Prize for Physiology and Medicine with Elie Metchnikoff. 3Jenner, Edward (1749-1823), British physician and naturalist, famous for his discovery of a vaccination against smallpox. After training under the surgeon John Hunter in London, Jenner set up in 1773 as a medical practitioner in Berkeley, Gloucestershire.

Jenner observed that infection with the mild disease called cowpox made people immune to smallpox. In 1796 he performed the vaccination by inserting cowpox matter into two scratches made on the arm of a healthy 8-year-old boy. A few months later the boy was inoculated with smallpox, and the disease refused to take. By 1800 some 100,000 people had been immunized, and a dramatic decrease in the death-rate from smallpox resulted. The practice met with some opposition, but before Jenner’s death, smallpox vaccination became practised throughout the world.

Jenner was a keen naturalist. His continued observation of animal life led him to describe the behaviour of the baby cuckoo, and to show the value of worms in arable soil. He also helped in the preparation and arrangement of specimens brought back to England by Joseph Banks in 1771. Kitasato Shibasaburo (1852-1931), Japanese physician and bacteriologist. From 1885 to 1891 he worked in the bacteriologist Robert Koch’s laboratory in Germany, and, together with Emil von Behring, developed an anti-toxin for immunization against diphtheria.

On returning to Japan, he founded an institutpublic health, a speciality within medicine that aims to identify and prevent the environmental and social causes of ill health. It is based on epidemiology, the study of disease within a population. The traditional concerns of public health include sanitation and water supply, air and noise pollution, food hygiene, nutrition, housing conditions, and the health and safety of people at work. More recently, public health doctors have also examined the health consequences of social problems such as unemployment and poverty.

Where other branches of medicine concentrate on the individual, public health focuses on groups and society as a whole. In affluent countries, problems are often tackled by preventive medicine, and by government regulations, which set standards in everything from food-processing to machinery noise. Sophisticated public health laboratories are also used to identify health hazards, to monitor outbreaks of infectious diseases such as Aids or influenza, or to trace the source in episodes of food poisoning.

It is generally agreed that most of the major advances in life expectancy in developed countries over the last century have been due mainly to improvements in public health, rather than to the efforts of curative medicine. Likewise, most of the current health problems in developing countries can be attributed to poor public health. 4e for the study of infectious diseases, and in 1894 discovered the infectious agent of bubonic plague5 World Health Organization (WHO), a United Nations specialized agency established in 1948 with the broad aim of attaining the highest level of health for all people, and supported by about 160 countries.

Its head office is in Geneva, Switzerland. WHO does not conduct its own research but promotes biomedical and health research in some 500 collaborating centres worldwide, arranging international medical conferences and the exchange and training of research workers. WHO compiles the International Pharmacopaeia, monitors epidemics, evaluates new drugs, and advises on biological standards. It publishes quarterly an international journal of health development (World Health Forum) in Arabic, Chinese, English, French, Russian, and Spanish.

A notable success of WHO has been the eradication of smallpox throughout the world. WHO advocates a number of public health measures to provide safe drinking water and adequate sanitation, the immunization of all children against major communicable diseases, and the reduction of malnutrition. In addition, it has intensified efforts to prevent and combat endemic diseases such as malaria and tuberculosis, and to give access to essential drugs and to family planning services. communicable disease (contagious disease, infectious disease), an infection which can be transmitted from person to person.

The individual with the infection is known as the carrier, who may or may not have the symptoms and manifestations of the infection. The modes of transmission are diverse, and include personal contact; inhalation of infected droplets derived from coughing or sneezing; ingestion of water or food contaminated with human sewage containing micro-organisms which are capable of causing disease (pathogens); sexual contact causing sexually-transmitted disease; use of contaminated injection and surgical equipment; use of infected blood or blood products; and contact with inanimate objects that the carrier may have used (fomites).

Communicable diseases may have to be reported to health authorities (notifiable diseases) for the purpose of initiating a rapid and effective response to contain the disease before widespread transmission. Infections that are notifiable include cholera, poliomyelitis, and tuberculosis. At the beginning of the 19th century the belief that communicable diseases were caused by ‘miasmata’, poisonous vapours given off by sewage and rubbish, led to campaigns to improve public health by supplying clean water and drainage systems.

In Britain this resulted in the Public Health Act (1848) drawn up by Edwin Chadwick, in the same year that the London doctor, John Snow, showed that cholera was carried by dirty water. In the latter half of the 19th century, Louis Pasteur, Heinrich Koch, and others began to identify the micro-organisms that caused infectious diseases and this led to further research into their prevention and cure. Vaccination against smallpox, first described by Edward Jenner in 1798, resulted in its global eradication by 1979.

The now routine use of vaccines against other common infectious diseases, including polio, diphtheria, tetanus, measles, and German measles, has greatly limited their spread. In the 20th century drugs were developed that could cure many infectious diseases. In 1910 Paul Ehrlich introduced salvarsan, the first effective cure for syphilis and, following the development of sulphonamides in the 1930s and antibiotics in the 1940s (penicillin was first used in 1941), many life-threatening diseases caused by bacteria and fungi can now be treated, resulting in greater life expectancy.

However, the indiscriminate use of antibiotics has resulted in the development of resistant strains of bacteria and a resurgence of the infections they cause. In addition, antibiotics are ineffective against viruses and treatment for some virus infections has proved much more difficult; antiviral drugs have had limited success, notably in treating infections caused by herpes viruses. There is still no cure for influenza, an epidemic of which killed up to fifteen million people in 1918-19, nor for the HIV (human immunodeficiency virus) which can result in Aids (acquired immune deficiency syndrome), whose symptoms were first recognized in 1979.

Cures are still needed for some tropical parasitic diseases. The toll of sickness and death from communicable diseases is low in the wealthier countries of the world, but remains high in developing countries, as data from the World Health Organization show (see also epidemiology). Malaria poses a major threat, with an estimated 100 million acute cases a year. There are 8 million new cases of tuberculosis a year and 3 million die from it, many of them young adults. As a result of the epidemic of Aids, of which tuberculosis is a manifestation, its incidence is increasing rapidly, particularly in Africa.

Many communicable diseases are chronic, with the result that debilitated sufferers are a constant source of reinfection. Among these are amoebic dysentery, with which WHO believes 400 million are infected, and schistosomiasis (bilharsiasis), with which 200 million are infected. Even where it seems that diseases have disappeared, they may reoccur, as the major cholera epidemic in Peru, which broke out in 1991, the first there for a century, showed. 6 Chadwick, Sir Edwin (1800-90), British public health reformer.

A friend and disciple of Jeremy Bentham, he was the architect of the Poor Law Amendment Act (1834). His report for the royal commission set up in 1833 to investigate the conditions of work of factory children resulted in the passing of the Ten Hours Act. In 1840, concerned at the number of people driven into pauperism by the death of the breadwinner during the numerous outbreaks of cholera, he conducted on behalf of the Poor Law Commissioners an Inquiry into the Sanitary Condition of the Labouring Population, published in 1842.

As a result of this and subsequent agitation, an Act of 1848 gave municipalities powers to set up local boards of health, subject to Public Health Commissioners, among them Chadwick himself. During his term of office as Commissioner of the Board of Health (1848-54), he persuaded urban authorities to undertake major water, drainage, and slum clearance schemes to reduce disease. 7communicable disease (contagious disease, infectious disease), an infection which can be transmitted from person to person.

The individual with the infection is known as the carrier, who may or may not have the symptoms and manifestations of the infection. The modes of transmission are diverse, and include personal contact; inhalation of infected droplets derived from coughing or sneezing; ingestion of water or food contaminated with human sewage containing micro-organisms which are capable of causing disease (pathogens); sexual contact causing sexually-transmitted disease; use of contaminated injection and surgical equipment; use of infected blood or blood products; and contact with inanimate objects that the carrier may have used (fomites).

Communicable diseases may have to be reported to health authorities (notifiable diseases) for the purpose of initiating a rapid and effective response to contain the disease before widespread transmission. Infections that are notifiable include cholera, poliomyelitis, and tuberculosis. At the beginning of the 19th century the belief that communicable diseases were caused by ‘miasmata’, poisonous vapours given off by sewage and rubbish, led to campaigns to improve public health by supplying clean water and drainage systems.

In Britain this resulted in the Public Health Act (1848) drawn up by Edwin Chadwick, in the same year that the London doctor, John Snow, showed that cholera was carried by dirty water. In the latter half of the 19th century, Louis Pasteur, Heinrich Koch, and others began to identify the micro-organisms that caused infectious diseases and this led to further research into their prevention and cure. Vaccination against smallpox, first described by Edward Jenner in 1798, resulted in its global eradication by 1979.

The now routine use of vaccines against other common infectious diseases, including polio, diphtheria, tetanus, measles, and German measles, has greatly limited their spread. In the 20th century drugs were developed that could cure many infectious diseases. In 1910 Paul Ehrlich introduced salvarsan, the first effective cure for syphilis and, following the development of sulphonamides in the 1930s and antibiotics in the 1940s (penicillin was first used in 1941), many life-threatening diseases caused by bacteria and fungi can now be treated, resulting in greater life expectancy.

However, the indiscriminate use of antibiotics has resulted in the development of resistant strains of bacteria and a resurgence of the infections they cause. In addition, antibiotics are ineffective against viruses and treatment for some virus infections has proved much more difficult; antiviral drugs have had limited success, notably in treating infections caused by herpes viruses. There is still no cure for influenza, an epidemic of which killed up to fifteen million people in 1918-19, nor for the HIV (human immunodeficiency virus) which can result in Aids (acquired immune deficiency syndrome), whose symptoms were first recognized in 1979.

Cures are still needed for some tropical parasitic diseases. The toll of sickness and death from communicable diseases is low in the wealthier countries of the world, but remains high in developing countries, as data from the World Health Organization show (see also epidemiology). Malaria poses a major threat, with an estimated 100 million acute cases a year. There are 8 million new cases of tuberculosis a year and 3 million die from it, many of them young adults.

As a result of the epidemic of Aids, of which tuberculosis is a manifestation, its incidence is increasing rapidly, particularly in Africa. Many communicable diseases are chronic, with the result that debilitated sufferers are a constant source of reinfection. Among these are amoebic dysentery, with which WHO believes 400 million are infected, and schistosomiasis (bilharsiasis), with which 200 million are infected. Even where it seems that diseases have disappeared, they may reoccur, as the major cholera epidemic in Peru, which broke out in 1991, the first there for a century, showed.

Tagged In :

Get help with your homework

image
Haven't found the Essay You Want? Get your custom essay sample For Only $13.90/page

Sarah from CollectifbdpHi there, would you like to get such a paper? How about receiving a customized one?

Check it out