Science & Technology in Action

4th Edition

The MMR Vaccine

Health Service Executive

Vaccines trigger the body’s immune system to produce antibodies without causing any disease. Memory cells ‘remember’ how to respond and so, in the event of a later infection, the body can respond much more effectively to a particular infection.
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Contains the full lesson along with a supporting toolkit, including teachers’ notes.

Lesson excerpt

Infection and Disease
The human body is constantly under attack by diseasecausingorganisms called pathogens. Many of these pathogens are tinymicrobes, such as bacteria and viruses that try to enter our bodies and live within. The invasion of the body by pathogens is called infection.

How the body prevents infection
The human body has several ways of defending itself. The first line of defence is the presence of physical and chemical barriers that prevent pathogens getting into the body tissues. This is also known as the general defence system; it includes the skin, mucus in the breathing passages, blood clotting at a wound and acid in the stomach – all of which inhibit the entry of harmful microbes.

Once the tissues have been invaded by a pathogen, a second, more specific defence system known as the immune response takes over. The immune system involves a number of different types of white blood cells, such as the phagocytes andlymphocytes as well as specialised organs of the body including the spleen, thymus and the lymph glands. The phagocytes, also known as macrophages, are large white blood cells that engulf and destroy harmful bacteria and viruses.

The lymphocytes provide a more specialised protection. Because the membranes of all cells are covered with special ‘marker’ chemicals called antigens, it is important for the body to be able to distinguish between its own cells and ‘foreign’ cells. When apathogen enters the body, the immune system responds by making a specific antibody to the ‘foreign’ antigen. Antibodies generally work by causing the pathogens to clump together and this enables the phagocytes to engulf and destroy them.

The type of antibody made depends on the type of antigen invading. For example an invading cold virus antigen will stimulate the production of a cold virus antibody that will only destroy the cold virus.

Quiz questions

  1. Since rubella affects unborn babies of pregnant women, only girls need be vaccinated against rubella. false
  2. Vaccination gives you the disease. false
  3. Antibodies are produced in response to antigens. true
  4. Lymphocytes and phagocytes are types of red blood cell. false
  5. The MMR vaccine works by stimulating the immune system to produce antigens against these diseases. false
  6. If 80% of the population are vaccinated, measles, mumps and rubella will be eradicated. false
  7. Measles is not fatal. false
  8. Measles, mumps and rubella have become less common since the vaccine was introduced. true
  9. Epidemics are most likely when vaccination levels are not sufficiently high. true