Immunisation – protecting our children from diseaseThe latest figures show that 91 per cent of Australian children are immunised. This is a vast improvement over the 53 per cent recorded in 1995. Key text Back to basics You will get more from this topic if you have mastered the basics of the immune system – this link will take you to an annotated list of sites with helpful background information. Key textIn 1995 the Australian Bureau of Statistics released a report showing that only 53 per cent of children aged between 3 months and 6 years were fully immunised against a range of potentially fatal diseases. This rate was one of the lowest in the developed world. A major government initiative – the Immunise Australia Program – has dramatically increased immunisation levels. A 2006 study showed that 91 per cent of 1-year-old children are fully immunised.Many childhood diseases can spread very quickly and have serious consequences. The improvement in the levels of immunisation should help Australia avoid new epidemics of vaccine-preventable diseases. The immune system To understand immunisation, we need first to understand the way in which the human body naturally protects itself against disease. Diseases come in many forms: some of the most lethal are caused by microorganisms such as bacteria, viruses and micro-parasites. To combat infection by these microorganisms, the body's immune system can marshal two main lines of defence – innate or natural immunity, and acquired immunity. These two lines of defence have different characteristics:
Vaccines In 1796, Edward Jenner achieved protection against smallpox by infecting James Phipps with another strain of pox virus (Box 2: Smallpox – the eradication of a disease). This became the first widely used vaccine. More than 200 years later, highly effective and safe vaccines are available to protect against diseases caused by many viruses and bacteria (Box 3: The basics of making a vaccine). Some vaccines, such as many attenuated viruses (eg, yellow fever, measles) need only be administered once or twice to achieve long-lasting immunity. Others, especially vaccines that don't use the whole microorganism (subunit or acellular vaccines), are less potent, and several doses may need to be administered over a considerable time period, sometimes several years. How effective is immunisation? It is important to recognise that the body's immune response is genetically determined. No matter how healthy a person is, they may respond very well to some vaccines but not to others. For example, one person may be fully immunised against measles after receiving the measles vaccine, but will not be fully immunised against mumps after receiving the mumps vaccine. Thus, in a given population, no vaccine will be 100 per cent effective: if a disease is prevalent in a community, some people who have been vaccinated will probably contract it. In Australia, the polio, measles and Haemophilus influenza type b vaccines protect about 95 per cent of those vaccinated; the diphtheria and whooping cough vaccines about 85 per cent; and the influenza virus vaccine about 70 per cent. The new acellular whooping cough vaccine may be slightly less effective than the traditional vaccine made from a killed, whole microorganism, but it gives fewer side-effects. A comprehensive vaccination program will limit the spread of a disease among a population, reducing the risk that non-immune people (ie, those people who have not been vaccinated and those who were vaccinated but whose immune systems did not respond to the vaccine) will become infected. This is known as ‘herd immunity’; eventually, when the number of non-immune people drops to a certain level, the disease will disappear from the population. For a highly infectious virus such as measles, about 95 per cent of people need to be immunised; for smallpox, which was less infectious, the figure was closer to 80 per cent. Disease eradication A global vaccination program can result in the eradication of a disease that only affects humans. This is how smallpox was beaten. It was declared eradicated from the world in 1980 by the World Health Organization (Box 2). Following intensive immunisation programs, indigenous poliomyelitis was eliminated from the whole of the Americas in 1994, and the last case occurred in China in 1995. Indigenous measles has recently been eliminated from Finland and the Caribbean Islands, and in the Americas the only confirmed cases in 2003 were people who had contracted the disease elsewhere (Box 4: WHO's Global Programme for Vaccines and Immunization). What are the risks? Like many other voluntary activities, such as driving cars or motor cycles, vaccination is not completely risk-free. The oral polio vaccine may cause poliomyelitis in about 1 in every million vaccinees; this is a tiny fraction of the number of healthy children who suffered (with many deaths) from this disease before vaccination was introduced. The traditional whooping cough vaccine causes some side-effects, most of which are minor. It has been accused of causing brain damage in about 1 in every 200,000 vaccinees but the causal relationship claimed was not accepted in a recent UK law case. In the UK in the late 1970s, the level of vaccination dropped from more than 80 per cent to 30 per cent following a media program about adverse reactions associated with this vaccine. Over the next 10 years there were two epidemics of whooping cough, each with some deaths and over 50,000 cases of the disease. By the early 1990s an intense vaccination campaign resulted in an immunisation rate of more than 90 per cent and there were very few cases of the disease reported. The use of the traditional whooping cough vaccine was suspended in Sweden in 1979 because of safety concerns. Many trials of different acellular vaccines were then carried out in Sweden in the ensuing years because of the resulting increased incidence of whooping cough. Now, many developed countries, including Sweden, the USA and Australia, have introduced acellular whooping cough vaccines to replace the traditional vaccine.
Vaccine safety has been examined in great detail in recent years by expert committees such as those convened by the US Institute of Medicine. Their findings show that the risks of side-effects are generally extraordinarily low. Not immune to criticism Since Edward Jenner's experiment, vaccination has had its share of controversy. Different groups have protested and argued against this practice. Yet the weight of scientific evidence is overwhelmingly in favour of immunisation (Box 5: A controversial history). Parents should be aware that there are some rare complications that can result from vaccination. A far greater risk, though, will arise if the immunisation rate against these diseases continues to fall. It is only when immunisation rates are high that Australian children will be protected against polio, diphtheria, whooping cough or tetanus, diseases that only a few decades ago were greatly feared. We have already had a taste of low immunisation levels with the recent outbreak of whooping cough; we need a shot in the arm – or maybe several – if we’re to halt such diseases in their tracks. Related Nova topics: Bird flu – the pandemic clock is ticking Kissing the Epstein-Barr virus goodbye? Warmer and sicker? Global warming and human health
Antibodies Antibodies are protein molecules that move freely in the bloodstream. They are manufactured by white blood cells in response to the presence of molecules on the surface of the disease-causing microorganism. These molecules are known as antigens. A particular antibody will combine best with the antigen that caused the production of that antibody: thus, the antibody is said to be specific for its antigen. Antibodies react chemically with these antigens in such a way that the microorganism or toxin is neutralised and destroyed before a cell is infected. T-cells At the cellular level, the body manufactures what are known as cytotoxic T lymphocytes – T-cells. These white blood cells recognise certain antigens produced by microorganisms and kill cells that harbour them. If an invading microorganism evades the antibodies and infects a cell, the T-cells will recognise the infected cell and kill it. Thus the two weapons of acquired immunity, the antibody and the T-cell, complement each other. Thanks for the memory Once an infection has been overcome, antibodies and T-cells remain in the body, often for years and sometimes for life, acting as a kind of ‘memory’. If the microorganism attacks again, these antibodies ‘remember’ it. They combine with the antigens on the surface of the microorganism and immobilise it so it is no longer able to damage cells in the body. If, despite the efforts of the antibodies, some cells in the body become infected, the memory T-cells are mobilised rapidly to kill the infected cells. Thus, the body has acquired immunity against that particular disease. Active immunisation Vaccination works by introducing harmless versions of a disease-causing microorganism or certain antigens of it to the immune systems of uninfected individuals. This ‘tricks’ the immune system into producing antibodies and, when required, T-cells specific to the microorganism. The body is thus equipped with the right armory should infection by the real microorganism occur. The vaccines used in vaccination are of several types:
Passive immunisation Protection against some infections may be achieved by passive immunisation. With this type of immunisation, antibodies produced in one person are introduced into another. These antibodies are injected into the host shortly before the expected exposure to a disease-causing microorganism. The antibodies are obtained from the blood plasma of people who have had the disease (or have been immunised against it). Injection of the antibodies confers immediate protection against infection for a short time (weeks). It may also be effective if given shortly after such exposure; for example, after being bitten by a snake or rabid dog. Related site
Smallpox has been eradicated In recent years, smallpox vaccine made from a similar virus, the vaccinia virus, has been used worldwide and smallpox has been eliminated altogether. The world’s last reported case was the death of a British laboratory worker who became infected with live smallpox virus kept at a research institution. Stores of smallpox Since smallpox has been eradicated as a disease, the only sources of the virus are stored in a couple of high-containment laboratories. A specialist committee of the World Health Organization (WHO) suggested destroying these stores of the virus in 1986. However, a project to look at the DNA of the virus forstalled the destruction of the stores. Now scientists are voicing arguments for and against the elimination of the virus. The most compelling argument for the destruction of the smallpox stores is the potential for terrorists to use the virus for biological warfare. Those against the destruction of the stores want the virus samples to be maintained for study. Australian scientist Professor Frank Fenner, chairman of the WHO committee involved in the decision, maintains that the responsible action is to destroy the virus. (Even if the virus is destroyed, doses of the smallpox vaccine would be kept.) In 2002 WHO voted to stop the destruction of remaining smallpox virus supplies. Stock of the virus will be used for research into new treatments and vaccines. No date has been set for any future destruction of the virus stock. Footnote:
Was Jenner unethical?
Some people think that Jenner was wrong to try deliberately to infect a
young boy with smallpox. At first glance, it seems as if Jenner callously
used a small child as a human ‘guineapig’.
Variolation
What Jenner did was actually not new; he carried out a practice called variolation,
which was common in his time. Variolation worked this way. When a person
was fit and healthy, they could be infected deliberately with smallpox because
they would then have a better chance of surviving. It is quite likely that
the ‘variolus matter’ (pus) was taken from people who were fairly healthy
themselves, so the virus they used would probably be a weakened strain.
Certainly the method worked, and it was very popular. However, variolation
was risky because people in contact with the variolated person could catch
smallpox and a few variolated people got such a severe case of smallpox
that they died. So while variolation was a fair bet, vaccination was a
much safer bet.
What Jenner did was to treat the small boy with cowpox first, and then
to variolate him in the normal way. When the boy did not develop smallpox,
he knew he had found a method that was safer than variolation. At no time,
then, did Jenner act in an unethical way.
Related sites
To make vaccines that produce the mild form of a disease, the disease-causing agent (the pathogen) must first be isolated and then treated so that it stimulates an immune response in the body but does not cause the disease. Obtaining the pathogen Conventional methods of producing vaccines involve growing large quantities of the pathogen. Viruses, for example, are cultivated by infecting cells grown in tissue culture, while many bacteria can be grown on agar gels. The pathogen is then concentrated, purified and treated to inactivate its capacity to cause disease. Inactivating the pathogen The pathogen can be inactivated using one of several techniques:
Adjuvants Most killed vaccines do not work unless an adjuvant is added. Adjuvants strengthen the immune response in some way. Most adjuvants currently used are compounds containing aluminium. New vaccines Medical researchers continue to pursue new methods of producing vaccines, particularly using biotechnology and genetic engineering techniques. These techniques can eliminate the need to produce large quantities of the microorganism in order to make a vaccine. Related sites
Two hundred years after Edward Jenner's introduction of vaccination against smallpox, and 20 years after the total eradication of this dreadful scourge from the world, it is opportune to ask how true the world has been to the Jennerian legacy. Are all the world's children reaping the benefits of immunization, arguably history's most cost-effective public health tool? The answer must be probed at three levels:
To put the matter into perspective, the following statistics are of relevance:
The most encouraging progress has been made in the case of poliomyelitis, where there is a very good chance of total eradication by the year 2000. The industrialized countries have been essentially free of polio for quite a few years. Polio transmission has ceased in the Western hemisphere, and there has also been no case of natural polio in any American country over the past 5 years. Bearing in mind how poor some of these countries are, this is a great public health triumph and a tribute not only to WHO and UNICEF, but also to Rotary International through their Polio Plus Campaign, and to the health ministries of the Latin American countries. As a result of this success, many other countries have buckled down to the task of polio eradication, the chief tool being "National Immunization Days" to supplement regular infant immunization programs. On a National Immunization Day, all children under 5 years of age receive the oral poliomyelitis vaccine, regardless of their previous vaccination history. This is a very powerful tool in breaking transmission chains. Highly successful National Immunization Days have been held in China and India. It is hoped that the Western Pacific Region, including China, will be polio-free within a year or two, leaving India and particularly Subsaharan Africa as the remaining very major challenges. The success of polio eradication in the Americas has posed an interesting problem for richer countries like the United States. Given that there is no more natural polio transmission, many feel that the very occasional (perhaps one in a million) reversion to virulence of the oral polio vaccine represents an unacceptable risk. United States citizens are therefore to be offered Salk-type inactivated polio vaccine as two injections prior to two further doses or oral polio vaccine (and in some instances even four inactivated polio vaccine shots). While this is more expensive than the oral vaccine, the cost differential is not a major factor in a rich country. The oral vaccine remains the favored tool in developing countries. There has also been great progress in measles control, and again a significant number of Latin American countries appear to have achieved total eradication. Here, interestingly, the industrial world is lagging behind, although the United Kingdom has recently succeeded in essentially wiping out measles infection (although sporadic imported cases still occur). Many feel that measles, which still has a 2-3% mortality in developing countries, should be the next disease targeted for eradication once polio is gone. Neonatal tetanus remains a big problem in countries where obstetric hygiene is defective. Here the task is to immunize pregnant women so that antibodies can cross the placenta and protect the infant. A tremendous help here would be "one-shot" vaccines because it is sometimes difficult to persuade women to return for booster injections. Unfortunately, the BCG vaccine has proven to be not as good as was originally hoped. It does do a good job in protecting infants from tuberculous meningitis and miliary tuberculosis, but the protection is clearly not strong enough to safeguard against pulmonary tuberculosis in young adult life. A better vaccine is badly needed. Hepatitis B is a recent addition to the list of vaccines in the WHO program. Although the costs have come down sharply since the first introduction of this excellent vaccine, they still remain an order of magnitude higher than the other vaccines on our list, so new resources are badly needed. One advantageous feature will be transfer of vaccine-producing technology to some of the larger developing countries, thereby solving hard currency problems. The challenge of newly introduced vaccines Beyond the eight vaccines discussed above, it will be imperative to make available to the developing countries some of the newer vaccines that have emerged from the research pipeline. One excellent example is Haemophilus influenzae B, or HIB, vaccine against meningitis. This sophisticated vaccine is a conjugate which appropriately stimulates T-cell-B-cell collaboration and has proven remarkably effective against the major cause of bacterial meningitis. In a recent trial in The Gambia, it has also proven effective against other forms of invasive HIB disease, such as HIB pneumonia. Once again, resources will have to be raised to enable this vaccine to be more widely delivered. Similar conjugate vaccines should soon be available for meningococci and pneumococci. Within this category of emerging vaccines there are also new and much more effective vaccines against cholera, typhoid, and perhaps other diarrheal diseases such as bacillary dysentery. As yet, it is unclear whether funds will be available to deploy such vaccines throughout the countries that most need them. SAGE and WHO are working with industry in an attempt to introduce tiered pricing, with countries being divided into five bands according to their degree of affluence or poverty. It is felt that many countries will need only encouragement and persuasion, whereas others may need virtually the whole cost of the vaccines to be subsidized through the international aid system. Vaccine research and development Both academic laboratories and industry appear to have got a "second wind" with respect to vaccine research and development. As a result, there are exciting developments both with respect to diseases for which vaccines are being actively sought and with respect to new ideas about vaccine delivery. In the former category there are extremely difficult problems, such as malaria and HIB, but also more accessible developments, such as rotavirus diarrhea, respiratory syncytial virus, dengue, and new approaches to a tuberculosis vaccine. With regard to the latter area at least five new developments could be mentioned:
The Global Programme for Vaccines and Immunization is not too likely to run out of work to do! That being said, it seems certain that within 20 years the situation with regard to communicable diseases globally will have improved very measurably. Prevention is not only better than cure – it is also much cheaper. With the health expenditure globally being under very great strain, this is no trivial point.
Opposition to vaccination in the past The practice of vaccination has always had its share of controversy. In 1806 John Birch, Surgeon Extraordinary to the Prince of Wales and Surgeon to St Thomas’s Hospital in London, wrote a paper entitled Serious reasons for uniformly opposing the practice of vaccination. He predicted that ‘we shall soon see what yet remains of popular opinion favourable to the cause of [smallpox] vaccination, vanish into thin air’. Instead the disease itself has vanished. A hundred years later, in 1913, Britain’s National Anti-Vaccination League published a booklet entitled Is vaccination a disastrous delusion? The booklet condemned the practice as ‘a monstrous and indefensible outrage upon the common sense and sacred personal rights of every human being, and especially every Englishman’. Current opposition to vaccination The issue of vaccination is still controversial. Many developed countries have small groups of people who are anti-vaccination and often highly vocal. Some are parents with a child who has had an illness in the weeks following vaccination, especially with the traditional whooping cough vaccine made from a killed, whole microorganism. The illness may have been caused by the vaccine, or it may have been a coincidence. Though some may be highly educated, very few in the anti-vaccine lobby have expertise in infectious diseases and immunology. It is entirely appropriate for parents to be concerned about the risks of vaccination, but they must be given the full facts. Major medical bodies support vaccination All the major medical bodies, including the World Health Organization and national medical associations, have been very strong supporters of vaccination. Some countries such as the USA have formed National Vaccine Advisory Committees, and in the USA unvaccinated schoolchildren are not accepted in schools (with rare exceptions). Particularly in many developing countries, there are national immunisation days when millions of infants and young children are immunised. The case for carrying out vaccination programs is strengthened by the increasing amount of solid evidence that they work, as exemplified by the smallpox, polio and measles eradication campaigns. The recent outbreaks of whooping cough and measles in Australia show that this country will lose its reputation for high standards of public health unless vaccination coverage is rapidly increased. Related sites
Materials (for each student)
Safety notes:
Questions
Teachers notes Background information Phenol red is an indicator solution that turns pink or red in alkalis. The ‘infected’ stock solution is 0.1 M sodium hydroxide (NaOH). This concentration should produce a pH that will ensure that even the diluted ‘infected’ solutions will turn red in phenol red. All of the ‘uninfected’ solutions should be yellow in the presence of phenol red. Because the pH of tap water varies, dilute (0.001 M) hydrochloric acid (HCl) is used as the ‘uninfected’ stock solution to ensure ‘uninfected’ samples turn yellow in phenol red. Also ensure that the test tubes do not have residual traces of acids or alkalis. Preparation This activity depends on one student in the class having an 'infected' solution that will turn red when phenol red is added. Set up test tubes to be collected so that one tube contains 0.1 M NaOH and all the others contain 0.001 M HCl.
Answers to questions
Notes Make sure that students understand the procedure before beginning. It is possible to make a number of variations to this activity:
You should be able to find information about some or all of the following aspects of the disease:
Teachers notes If students have difficulty selecting a disease, you could suggest one of the following: malaria, smallpox, polio, whooping cough (pertussis), diphtheria, chicken pox, measles, rubella, glandular fever, tuberculosis, typhoid, mumps, tetanus, yellow fever, influenza, hepatitis A, B, or C, AIDS, pneumonia, herpes, anthrax, cholera, Ebola virus, Legionnaire’s disease, Murray Valley encephalitis, epidemic polyarthritis (Ross River fever), rheumatic fever, amoebic dysentery, typhus, chlamydia, syphilis, gonorrhoea.
Australasian Science March 2005, pages 38-40 War of the worms (by Joanne Lello) Suggests that interactions between different parasitic species in the intestine can influence the effectiveness of vaccines.
September 2004, page 41 HIV outwits vaccine researchers (by Simon Grose) Reveals why a vaccine for HIV is still decades away.
Nature A collection of Nature articles on the eradication of polio is available.
2 February 2006, page 509 When a vaccine is safe Comments on the public acceptance of a vaccine for Lyme disease.
2 February 2006, pages 524-525 Lyme disease: Uphill struggle (by Alison Abbott) An in-depth article about Lyme disease and the development of a vaccine.
26 June 2003, pages 912-914 AIDS vaccines: Back to 'plan A' (by Erika Check) Discusses the revival of the antibody strategy in AIDS vaccine research.
New Scientist 7 June 2008, page 12 Hay fever vaccine needs just four shots (by Andy Coghlan) Reports on development of a vaccine for hay fever
4 February 2007, page 12 Vaccine zaps allergy in record time (by Aria Pearson) Looks at the development of new vaccines for allergy sufferers that are effective within a few weeks.
27 January 2007, page 9 Vaccines set to target immune panic button (by Andy Coghlan) Describes a new type of vaccine that recruits the immune system to enhance their effectiveness.
25 November 2006, page 10 Beefed-up vaccine hits back at polio (by Debora Mackenzie and Linda Geddes) Reports on a new vaccine to eradicate polio in areas where the traditional vaccine is not effective.
14 October 2006, pages 21-23 Friend or foe? (by Peter Aldhous) Looks at the dilemma caused by research into new vaccines and drugs that can be used in biowarfare.
23 September 2006, page 13 If it stops plague, will it stop hospital superbugs? (by Deborah MacKenzie) Looks at a way to make vaccines against many different pathogens.
19 August 2006, page 12 Vaccine to fend off HIV moves a step closer (by Roxanne Khamsi) Discusses the possibility of an HIV vaccine containing ‘boosted’ immune cells.
27 July 2006, page 8 Eradicating polio leaves people defenceless (by Debora MacKenzie) Reports that the number of polio cases is increasing in some areas.
1 July 2006, page 20 Killer tomatoes attack disease (by Andy Coghlan) Describes genetically modified tomatoes that contain an edible vaccine.
3 June 2006, page 16 ‘Alien code’ leads to faster vaccines (by Peter Aldhous) Describes the use of a modified three letter code for virus genes to make a weakened virus, which is suitable for a vaccine.
29 April 2006, pages 12-13 Vaccines at birth come a step closer (by Bob Holmes) Looks at a way to vaccinate new born babies, which is particularly important in poorer countries.
18 March 2006, page 7 Africa leads measles purge Provides an update on the progress of a measles vaccination campaign in Africa.
9 March 2006, page 12 Vaccine could stop MS in its tracks (by Andy Coghlan) Describes the trial of a vaccine that destroys the white blood cells that attack myelin.
14 January 2006, page 17 Rotavirus vaccines set to slash infant deaths (by Alison Motluk) Describes two new vaccines to prevent death from diarrhoea in children.
19 March 2005, page 42-45 The cure that came in from the cold (by Robin Orwant) Covers the comeback of serum therapy as a method of vaccination.
5 March 2005, page 16 Ending MMR shots does not halt rise in autism (by Andy Coghlan) Comments on the results of a study of more than 30,000 children on the effect of the MMR vaccine on autism.
19 February 2005, page 3 The temptation of edible vaccines Comments on the risk of edible vaccines finding their way into the human food chain.
19 February 2005, page 19 Why vaccination by potato got chopped Argues that a vaccine made in genetically modified potatoes was abandoned because of fears that 'pharm' crops could be mixed with normal produce.
19 February 2005, page 42 Vaccines for pennies (by James Randerson) The story of an Indian husband and wife team who built a facility to produce a hepatitis B vaccine.
3 February 2001, pages 8-11 MMR vaccine: A special report A series of articles on the possible link between the combined measles, mumps and rubella vaccine and some cases of autism.
5 February 2000, pages 20-21 Down but not out (by Debora MacKenzie) Discusses the feasibility of a campaign to eradicate polio by 2005.
Scientific American May, 2008, pages 74-75 Can this man beat the flu with a single universal vaccine? (by Alexander Hellemans) Reports on research that could help to develop a universal flu vaccine.
3 January 2007 How much AIDS vaccine do poor countries really want? (by JR Minkel) Reports on efforts by public health groups to understand the factors that influence the use of vaccines in developing countries.
October 2006, pages 34-40 Peacekeepers (by Zoltan Fehervari and Shimon Sakaguchi) Manipulations of regulatory T cells could offer new treatments for conditions ranging from diabetes to organ rejection.
26 July 2006 Irradiated pathogens used to create potent vaccine (by David Biello) Suggests that irradiated microorganisms trigger a strong immune response.
July 2006, pages 23-24 Dangling a carrot for vaccines (by JR Minkel) Suggests ways to get companies interested in making vaccines for developing countries.
April 2006, pages 33-39 New hope for defeating rotavirus (by Roger Glass) Provides a brief history of rotavirus research and breakthroughs in vaccine development.
April 2006, page 13 Turning yellow (by Christine Soares) Looks at efforts to use the yellow fever vaccine against other diseases.
10 January 2006 Tobacco plant transformed into plague vaccine factory (by David Biello) Describes the use of plants to produce a vaccine against plague.
9 May 2005 Defensive eating (by Luis Miguel Ariza) Discusses some of the concerns about food vaccines.
20 May 2002 Special delivery (by Gary Stix) The bioterror weapon of choice has supplied new treatment strategies for HIV and cancer.
September 2000, pages 48-53 Edible vaccines (by William H.R. Langridge)
July 1999, pages 34-41 Genetic vaccines (by David B. Weiner and Ronald C. Kennedy) Vaccines crafted from genetic material might one day prevent AIDS, malaria and other devastating infections that defy current immunization technologies. They may even help treat cancer.
TIME Magazine 21 January 2002 Vaccines stage a comeback (by Michael Lemonick and Alice Park) They defeated some of the deadliest diseases known to man and may soon protect us from AIDs, Ebola, heart disease and even cancer.
Vaccines (Kimball Biology Pages, USA)
Includes information on different types of vaccines, a table of some of the most widely used vaccines, some problems of vaccine development and DNA vaccines.
Types of vaccines (Web Health Center)
Describes different types of vaccines including active immunization using live vaccines, inactivated vaccines, toxoids, cellular fractions as well as passive immunisation using immunoglobulins and antisera.
Vaccines – how and why? (Access Excellence, USA)
Includes the history of vaccination, how vaccines work and how they are made.
Immunisation (Better Health Channel, Australia)
Many illnesses, particularly those which affect children, can be prevented by immunisations.
Australian Broadcasting Corporation
antigen. Any foreign substance, usually a protein, that stimulates the body's immune system to produce antibodies. (The name antigen reflects its role in stimulating an immune response – antibody generating.) attenuated vaccines. Vaccines are designed to stimulate antibody production without causing serious disease. To make an attenuated vaccine, a disease-causing microorganism is first isolated and then attenuated (made less virulent) by ageing it or altering its growth conditions (such as by depriving it of an essential nutrient). The vaccines for measles, mumps, and rubella are prepared in this way. Because this vaccine is actually a living microbe, it multiplies within your body and therefore causes a strong stimulation of the immune system. bacterium (plural bacteria). A single-celled, microscopic organism without a distinct nucleus. immune system. The cells, tissues and organs that assist the body to resist infection and disease by producing antibodies and/or altered cells that inhibit the multiplication of the infectious agent and provide resistance to disease. immunisation. The process by which the body develops the capacity to combat a specific infection. Immunisation can be induced by introducing vaccines into the body. This is more correctly called vaccination or inoculation, but the word immunisation is used to mean the same thing. toxins. Substances, produced by microorganisms, which affect the functioning of another organism. vaccine. A preparation consisting of antigens of a disease-causing organism which, when introduced into the body, stimulates the production of specific antibodies or altered cells. This produces an immunity to the disease-causing organism. The antigen in the preparation can be whole disease-causing organisms (killed or weakened) or parts of these organisms. virus. A submicroscopic infectious agent consisting of a nucleic acid (DNA or RNA) molecule surrounded by a protein coat. Viruses cannot replicate outside a living cell. More information can be found at How viruses work (How Stuff Works, USA).
External sites are not endorsed by the Australian Academy of Science. Posted October 1997. The Australian Foundation for Science is also a supporter of Nova. This topic is sponsored by The
Walter and Eliza Hall Institute of Medical Research
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