Infection & ResponseTopic Summary
Knowledge Organiser
Part of Vaccination and Herd Immunity — GCSE Biology
This topic summary covers Knowledge Organiser within Vaccination and Herd Immunity for GCSE Biology. How vaccines work, types of vaccines, population immunity, vaccination programs It is section 14 of 15 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 14 of 15
Practice
18 questions
Recall
21 flashcards
Knowledge Organiser
How Vaccines Work
- Introduce antigens (from dead/weakened/component pathogen)
- Antigens activate specific B cells
- Clonal expansion produces plasma cells and memory B cells
- Memory B cells persist for years
- On real infection: rapid secondary response clears pathogen before symptoms
Herd Immunity Key Facts
- Threshold = 1 - (1/R₀)
- Measles: R₀ = 15, threshold = 93-95%
- Flu: R₀ = 2, threshold = 50%
- Protects those who cannot be vaccinated (babies, immunocompromised)
- Falls if coverage drops below threshold
Common Marks Lost
- Saying vaccines cause the disease (they do not)
- Not naming memory cells as key mechanism
- Confusing herd immunity with "everyone vaccinated"
- Not explaining WHO benefits from herd immunity
- Missing the formula for threshold or not showing working