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A Search For Better Health Topic 10: Vaccinations

A Search For Better Health Topic 10: Vaccinations

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A Search For Better Health Topic 10: Vaccinations

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  1. A Search For Better HealthTopic 10: Vaccinations Biology in Focus, HSC Course Glenda Childrawi, Margaret Robson and Stephanie Hollis

  2. DOT Point(s) • outline the way in which vaccinations prevent infection • process, analyse and present information from secondary sources to evaluate the effectiveness of vaccination programs in preventing the spread and occurrence of once common diseases, including smallpox, diphtheria and polio

  3. Introduction When an antigen is first encountered by the immune system, the time taken to fight the infection is quite long. This is because, once the antigen has been identified, the appropriate T cells and B cells have to be activated and then it takes time to build up clones of these cells.

  4. Introduction Time is also needed for the cytotoxic T cells to kill the infected cells and for the B cells to produce plasma cells that then secrete antibodies and bind with the antigen to neutralise it.

  5. Introduction If sufficient antibodies are made to destroy all the infecting antigens, the person recovers completely. This is known as the primary response. At the same time, memory T cells and memory B cells specific to the antigen are produced and remain in the body.

  6. Introduction If the same antigen were to re-enter the body in the future, the response, known as the secondary response, is much quicker. After identification of the antigen, the memory cells will activate the production of the cytotoxic T cells and the B cells.

  7. Introduction A very large number of B cells will then form many plasma cells, which secrete a much larger amount of antibodies than in the primary response. The effect of this is to destroy the invading antigens before their numbers are large enough to cause any symptoms.

  8. Introduction The secondary response: • is more rapid and requires less antigen to initiate it • produces a much greater quantity of antibodies • lasts for a longer period of time

  9. Introduction This type of immunity, where the immune response occurs and memory cells are produced, is called active acquired immunity. It is naturally induced as the body has to undergo the immune response and suffer the symptoms of the disease in order to develop immunity to it.

  10. Introduction Active acquired immunity can also be artificially induced through the use of vaccines, which cause the production of memory cells without the body experiencing the symptoms of the disease.

  11. Vaccinations Vaccines contain cultures of microorganisms, which may be either: • living but attenuated (weakened) and therefore harmless (rabies, poliomyelitis, measles), or • dead (typhoid, whooping cough). Vaccines may also contain modified toxins called toxoids (tetanus, diphtheria). These vaccines may be given orally, by injection or by scratching the skin surface.

  12. Vaccinations • Vaccines are all harmless to the body and will not cause the disease that they are specific for, but still contain the antigens that cause the body to undergo an immune response and produce memory cells for that particular antigen.

  13. Vaccinations • If the body is exposed to that antigen in the future, the secondary response will be activated and the antigen will be destroyed before any symptoms of the disease are experienced. The immunity formed in this way is usually lifelong. Each vaccine is specific for only one type of antigen and will therefore give immunity for only one type of disease.

  14. Vaccinations For a vaccine to be effective, a series of vaccinations should be given over a number of years. Each time the vaccine is introduced into the body, a small response is produced. Over a series of vaccinations the lymphocytes will more rapidly recognise the antigen and the numbers of memory cells produced will be enough to give immunity for a long time.

  15. Vaccinations In some cases, the numbers of memory cells decrease over time and booster injections have to be given to increase the number of circulating memory cells to ensure the immunity is maintained for that disease. For example, booster injections must be given to maintain immunity to tetanus as the number of memory cells for this decreases over time.

  16. Vaccinations Another type of acquired immunity is passive acquired immunity, which involves the introduction of antibodies (immunoglobulins) into the body to prevent a disease from developing. These antibodies have been produced by another organism that has suffered the disease.

  17. Vaccinations For example, if you have been exposed to the disease hepatitis A, you may be given injections of immunoglobulins (antibodies) to prevent you from contracting the disease. This immunity will last for only a couple of months as no memory cells have been produced.

  18. Vaccination Programs Before much was known about the cause, treatment and prevention of disease many people, including large numbers of children, lost their lives to diseases that today have been eradicated or the incidence of which is very low.

  19. Vaccination Programs Vaccination has been recognised as one of the most successful public health programs used to prevent disease. In 1974, the World Health Organization (WHO) launched the Expanded Program on Immunisation (EPI) to increase the percentage of the world’s infants immunised against the six target diseases: diphtheria, tetanus, whooping cough, polio, measles and tuberculosis. This increased the percentage of all infants immunised from 5% in 1974 to 80% in 1997, preventing around three million deaths each year.

  20. Vaccination Programs Mass immunisation programs not only prevent the occurrence of the disease in individuals, but also help to decrease the spread of the disease throughout the population. If the majority of the population is immunised against a disease, the chance of an infected individual coming into contact with an unprotected person is extremely low and the transmission of the disease is effectively stopped. This is known as the principle of ‘herd immunity’.

  21. Vaccination Programs Despite the success of vaccination programs there has recently been an increase in the number of cases of diseases such as pertussis (whooping cough). This is because a number of people are neglecting to get themselves or their children immunised.

  22. Vaccination Programs People are becoming complacent and thinking they will not contract the disease because of the low incidence in the population. They have also never experienced the seriousness of these diseases. Individuals may also refuse to have themselves or their children immunised because they feel the risks of side effects are too great.

  23. Vaccination Programs Smallpox, diphtheria and polio are three diseases that were very common in the world until the implementation of vaccination programs to try to prevent their spread and occurrence. Handout Table 5.1

  24. Smallpox Smallpox is caused by a virus that may be airborne or spread by direct contact. It enters the throat and lungs and causes a high fever and a blistering rash, which first appears on the face, arms and legs and eventually spreads over the entire body. It is often fatal. -

  25. Smallpox There have been numerous accounts in literature that smallpox first appeared more than 10 000 years ago and was spread around the world by explorers and traders. It was introduced into Mexico in 1519 and killed millions of people. The first recorded incidence of smallpox in Australia was in 1789 and had a devastating effect on the Aboriginal communities.

  26. Smallpox Smallpox has killed more people than any other infectious disease and was responsible for one-tenth of all deaths in Europe in the 19th century and more than 300 million deaths in the 20th century. Each year until 1968, there were 10–15 million cases of smallpox, resulting in two million deaths.

  27. Smallpox Edward Jenner developed a vaccine for smallpox in 1796, but it did not become effective because the procedure was not widely used. The vaccine was made available for free in Britain from the 1840s, but was still not widely used there until it became compulsory.

  28. Smallpox In 1967, there were still 33 countries in which smallpox was a problem. The overcrowding, extreme poverty, poor hygiene and poor nutrition were conditions present in these countries that increased the spread of this devastating disease.

  29. Smallpox The WHO committed itself to a worldwide mass immunisation program in order to eradicate the disease. This program involved routine mass immunisation, supplementary doses given on special immunisation days, targeting people who missed out on the routine immunisations and sending out special teams for surveillance on all possible cases of smallpox infection.

  30. Smallpox This program proved to be very successful, and in 1979 WHO declared that it had eliminated the virus from the world population and eradicated the disease smallpox. The only samples of the virus in the world today are in a couple of research laboratories where scientists are studying its DNA.

  31. Diphtheria Diphtheria is caused by highly contagious and fast-acting bacteria, often killing within a week of the start of symptoms. It is transmitted by close contact with respiratory droplets.

  32. Diphtheria It begins with a sore throat, fever and rapid pulse and then the destruction of the lining of the throat and the formation of a leathery membrane across the throat. This can lead to death by suffocation and, if not, then death can be caused by toxins, which cause damage to other organs such as the heart. Even if the patient recovers from the infection, they can be left with permanent nerve and heart problems.

  33. Diphtheria Prior to development of a vaccine, mortality rates were high, with 90% in diphtheria of the larynx; two-thirds of these were children under 5 years old. One hundred years ago diphtheria was referred to as ‘the deadly scourge of childhood’. In 1921 there were 206 000 cases with 15 500 deaths in the United States of America alone.

  34. Diphtheria A vaccine was released in 1923 but it was not until the 1940s–1950s that the cyclical epidemics were reduced to occasional outbreaks. Immunisation programs were introduced in Australia in the 1930s and 1940s and resulted in a rapid decrease in the incidence of diphtheria. Similar programs were also successful in Europe and other developed countries.

  35. Diphtheria In 1974 there were still only 5% of children immunised against diphtheria worldwide. The introduction of the WHO EPI saw the percentage of children immunised worldwide increase to 80% by 1990 (only 50% of children in Africa). This corresponded to a greatly decreased mortality rate reported worldwide.

  36. Diphtheria There has been only one reported case of diphtheria in Australia from 1994–2006. The current immunisation program involves the administration of the triple antigen—diphtheria, whooping cough and tetanus—at 2, 4 and 6 months and a booster injection at school entry and 15 years. There is the chance of a resurgence of the disease due to some people neglecting or refusing to vaccinate.

  37. Polio Polio, or poliomyelitis, is a viral disease that is transmitted by inhaling infected droplets and by direct contact. It causes fever and headache, speech, swallowing and breathing difficulties, and paralysis. Death occurs in 50% of the cases and nerve damage and paralysis in 50% of sufferers.

  38. Polio Polio first occurred thousands of years ago and, prior to the development of a vaccine by Jonas Salk in 1955, thousands of children died or were paralysed. In the years following the introduction of the vaccine, 200 people contracted the disease from the vaccine and 11 of them died. A safer vaccine developed by Albert Sabin was introduced and, after widespread immunisation, there was a 60–70% reduction in the disease.

  39. Polio Polio became very rare in industrialised nations, and the incidence further decreased after the EPI was introduced in 1974. In 1988, the World Health Assembly (WHA) voted to launch a global goal to eradicate polio. This Global Polio Eradication Initiative involved widespread vaccination of children under 5 years in countries where the disease was still endemic. In 1997, almost 450 million children under 5 years were immunised during National Immunisation Days.

  40. Polio There were 719 cases of wild poliovirus in 2000. This represents a 99% reduction in cases since the program began in 1988, with 350 000 estimated cases. Australia has had no reported cases of polio since 1988 and the current immunisation program involves oral Sabin vaccine at 2, 4 and 6 months and a booster at school entry and 15 years.

  41. Homework -Work on your Assessment Task