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
- Herd immunity: enough people immune so pathogen cannot spread through population
- Protects those who cannot be vaccinated: babies under 12 months, immunocompromised patients, elderly with weaker immune systems
- Falls if vaccination coverage drops โ outbreaks occur when threshold not met
- More contagious disease (e.g. measles) needs higher coverage than less contagious (e.g. flu)
- Measles needs ~95% coverage; flu needs ~50% coverage
Key Terms
- Vaccination โ introducing antigens to stimulate memory cell production without causing disease
- Herd immunity โ indirect protection of unvaccinated individuals when enough of population is immune
- Memory B cell โ long-lived white blood cell formed during primary response; enables rapid secondary response
- Primary response โ slow (5โ10 days), low antibody level, memory cells formed
- Secondary response โ fast (1โ3 days), high antibody level, pathogen cleared before symptoms
Common Marks Lost
- Saying vaccines cause the disease (they introduce antigens only โ dead/weakened/component pathogens)
- Not naming memory cells as the mechanism for long-term protection
- Confusing herd immunity with "everyone is vaccinated" โ unvaccinated people are indirectly protected
- Not naming WHO benefits from herd immunity (babies, immunocompromised, elderly)
- Saying booster doses are unnecessary โ antibody levels fall over time; boosters restimulate memory cells
This topic summary covers Knowledge Organiser: Vaccination and Herd Immunity within Vaccination and Herd Immunity for GCSE Biology. How vaccines work, types of vaccines, population immunity, vaccination programmes It is section 15 of 15 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Vaccination and Herd Immunity
What do vaccines contain?
Explain how vaccination protects a person from getting a disease. [3 marks]
Quick recall flashcards
What is a vaccine and how does it work?
A vaccine contains a dead or weakened form of a pathogen (or its antigens).
It triggers the immune system to produce antibodies and memory cells without causing disease.
If the real pathogen enters later, memory cells respond rapidly.
Why don't vaccines cause the disease they protect against?
Vaccines use dead or inactive pathogens, or just antigens from the pathogen's surface.
The pathogen cannot multiply or cause infection.
The immune system still recognises the antigens and builds immunity.