Vaccination programmes aim to protect large populations from infectious diseases. Explain why a person who has been vaccinated against a disease is protected if they are later exposed to the live pathogen.

WJEC GCSE Biology (Wales) — 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)

The vaccine contains antigens from the pathogen that are recognised as foreign by the immune system.
White blood cells (B‑cells) produce antibodies that are specific to those antigens.
During the primary response, memory B‑cells are created and remain in the body.
If the person is later exposed to the live pathogen, the memory cells recognise it immediately and trigger a rapid, large antibody response, preventing illness.

Examiner tips

  • Use the term ‘antigens’ and ‘memory cells’ – these are key words. Show the sequence: vaccine → antibody production → memory cells → rapid response. Keep the answer concise – 4 points, 1 sentence each.
  • common_mistakes
  • :
  • Confusing the vaccine with the live pathogen; the vaccine contains antigens, not the whole organism. Forgetting to mention memory cells or the speed/size of the secondary response.

Mark scheme (4 marks)

  1. The vaccine contains antigens (from the pathogen) which are recognised as foreign
  2. White blood cells produce antibodies specific to those antigens
  3. Memory cells are produced / remain in the body after the initial immune response
  4. On exposure to the live pathogen, memory cells allow a faster/larger antibody response so the person does not become ill

Key terms in this question

vaccination

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