Explain why a vaccine made from a dead or weakened pathogen can protect a person against the disease caused by the live pathogen.

Eduqas GCSE Biology — 2.6.2 The immune system · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

1. The vaccine contains a dead or weakened pathogen that still displays the same surface antigens as the live disease-causing organism.
2. These antigens are recognised by white blood cells, which then stimulate the production of specific antibodies.
3. The immune response also generates memory B‑cells and T‑cells that persist in the body.
4. When the real pathogen later infects the person, the memory cells recognise its antigens immediately, producing large amounts of antibodies quickly and preventing the disease from developing.

Examiner tips

  • Use the word ‘antigens’ and ‘antibodies’ – examiners look for correct terminology. Show the sequence: antigen → antibody production → memory cells → rapid response on re‑infection. Keep each point brief but complete – 4 marks allow one sentence per point.

Common mistakes

  • Confusing the vaccine with the live pathogen – remember the vaccine is dead/attenuated. Forgetting to mention memory cells or the rapid response. Using vague terms like ‘immune system’ without specifying antibodies or memory cells.

Mark scheme (4 marks)

  1. The dead or weakened pathogen still carries antigens
  2. The antigens stimulate white blood cells to produce antibodies
  3. Memory cells are produced that remain in the body
  4. If the live pathogen enters the body, memory cells respond quickly to produce large amounts of antibodies, preventing illness

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