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A series of free Science Lessons for 7th Grade and 8th Grade, KS3 and Checkpoint Science in preparation for GCSE and IGCSE Science.

Pathogens are microorganisms that cause infectious diseases.
White blood cells protect us from pathogens.
White blood cells produce antibodies which destroy particular bacteria or viruses.
Once we fight off a pathogen, we are immune. Immunity is specific.
Vaccination against a disease protects us from future infections by that specific pathogen.
White blood cells produce antibodies against the dead or inactive pathogen. If you are attacked by the live pathogen, you can now produce antibodies more rapidly, fighting off the pathogen.
To prevent the spread of a pathogen in a population, it is important that a very large number of people are vaccinated against the disease.

The Origin of Vaccines
Edward Jenner was an English scientist who lived in the 18th century. He discovered the first vaccine, which was for the smallpox virus. This disease was widespread in the 18th century and killed many people. Those who were infected but survived were often left badly scarred.

Jenner noticed that milkmaids who had caught the cowpox virus did not normally then catch smallpox. Cowpox was very similar to smallpox but less contagious.

He collected pus from the cowpox blisters on a milkmaid’s hands and purposefully infected a small boy. The boy was taken ill for a short while, but was then resistant to any subsequent infections of the cowpox and smallpox viruses. He tested this by infecting the boy with smallpox. No illness occurred. Jenner was therefore the first person to vaccinate someone against infection.

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