Explain how the body produces antibodies following a vaccination, and explain why a vaccinated person is protected if they later encounter the same pathogen.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
The vaccine contains antigens from the pathogen (either a dead or weakened form). White blood cells, mainly lymphocytes, recognise these antigens and produce antibodies that are complementary to them. During this primary response, some of the lymphocytes become memory cells that persist in the body. If the same pathogen later enters, the memory cells recognise its antigens immediately and trigger a rapid secondary response, producing large amounts of antibodies before the person becomes ill, thereby destroying the pathogen before symptoms develop.
Examiner tips
- Mention the vaccine’s antigens and the role of lymphocytes in antibody production
- Explain the formation and function of memory cells
- Show the rapid, large‑scale antibody response on re‑exposure
- Use correct terminology: antigens, antibodies, memory cells
Common mistakes
- Confusing antibodies with antigens
- Failing to mention memory cells or the rapid secondary response
- Using vague terms like "immune system" without specifics
Mark scheme (5 marks)
- The vaccine contains antigens (from the pathogen / dead or weakened pathogen)
- White blood cells / lymphocytes detect the antigens and produce antibodies complementary to / specific to those antigens
- Memory cells are produced / remain in the body after the initial immune response
- If the same pathogen enters the body again, memory cells recognise the antigens and respond rapidly
- Antibodies are produced in large quantities / before the person becomes ill, so the pathogen is destroyed before symptoms develop
Key terms in this question
Related
- All AQA A-Level Biology (7402) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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