Fighting Disease

There are 2 types of pathogen: Bacteria and Viruses.

Bacteria: Small living cells.

Very small and are 1/100th of the size of a human cell. They make you feel ill by producing toxins and damaging cells.


They are not cells, they are 1/100th the size of a bacterium. They replicate themselves by invading your cells a dusing the cells' machinery to produce many copies of themselves which then burst aned release many new viruses. The cell damage is what makes you feel ill.

Defence system:

Your skin, plus hairs and mucus in your respiratory tract stop pathogens from getting inside your body. Platelets try and prevent microorganisms getting inside your body through cuts by small fragments of cells clot the blood quickly to seal wounds. If something does make its way through your immune system kicks in. Your white blood cells travel around your blood and constantly look out for microbes. If it detects one there is 3 lines of defence.

  1. Consuming them: white blood cells engulf foreign cells and digest them
  2. Produce antibodies: Each invading cell has unique molecules (ANTIGENS) on its surface, when a white blood cell comes acorss a foreign cell they start to produce proteins called antibodies to kill invading cells. The antibodies produced are specific to the type of antigen. Antibodies are then produced rapidly and carried around the body to kill all similar bacteria/viruses. If the person is infected with the same pathogen again the white blood cells will rapidly produce the antibodies to kill it - the person is naturally immune to that pathogen and won't get i
  3. Produce anti-toxins: These counteract toxins produced by the invading bacteria.


Vaccination: Protects you from future infections

When you are infected with a new microorganism it takes your white blood cells a few days to learn how to deal with it, so you're ill for that amount of time.                                         Vaccinations involve injecting small amounts of dead or inactive microorganisms that carry antigens which cause your body to produce antibodies to attack them even though the microorganism is harmless. For example: MMR vaccine covers measles, mumps and rubella.    But if live microorganisms appear after that your white blood cells can mass-produce antibodies specific to that pathogen. However some vaccinations wear off after time so booster injections are needed.


  • Vaccines have helped control lots of infectious diseases that were once common (e.g. polio, measles, whooping cough..). Polio infections have decreased by 99%.
  • Big outbreaks of disease - epidemics - can be prevented if a large percentage of the population is vaccinated and is unlikely for the disease to be passed on.


  • Vaccines dont always work and sometimes dont give you immunity.
  • You can sometimes get bad side effects from the vaccine, e.g. fever, swelling, seizures, however these are very rare.
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