Describe how vaccination protects a person from becoming ill when they are later exposed to a pathogen.

Edexcel GCSE Biology (1BI0) — 5.2 Pathogens and immunity · Describe · 4 marks · View as Markdown

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

Model answer (4 marks)

The vaccine contains antigens from the pathogen (or a weakened or dead form of it). These antigens are recognised by B‑lymphocytes, which then produce antibodies that are specific to the antigen. The exposure also creates memory B‑cells. If the person is later exposed to the real pathogen, the memory cells recognise it immediately and the antibody response is rapid and large. The antibodies act quickly enough to destroy the pathogen before symptoms develop, so the person does not become ill.

Examiner tips

  • Use the exact terms – ‘antigens’, ‘B‑lymphocytes’, ‘antibodies’, ‘memory cells’.
  • Show the sequence: vaccine → antigen → B‑cell activation → antibody + memory cell → rapid response on re‑exposure.
  • Mention that the response is faster/stronger on re‑exposure.
  • Explain that antibodies destroy the pathogen before illness.

Common mistakes

  • Mixing up T‑cells for the antibody response; the question focuses on B‑cell/antibody action.
  • Failing to mention memory cells or the speed of the second response.
  • Using vague phrases like ‘immune system’ without specifying antibodies or memory cells.

Mark scheme (4 marks)

  1. The vaccine contains antigens (from the pathogen / a weakened or dead form of the pathogen)
  2. The antigens stimulate B-lymphocytes to produce antibodies specific to that antigen
  3. Memory cells are produced so the response on re-exposure is faster / larger
  4. Antibodies are produced quickly enough to destroy the pathogen before the person becomes ill (on re-exposure)

Key terms in this question

vaccination

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