C3.2.17—Herd immunity
Herd immunity explains how a specific barrier, pathogen interaction, immune mechanism or treatment response contributes to protection against infectious disease.
- Syllabus
- First assessment 2025
- Objective
- C3.2.17
- Level
- HL
Concept essentials
- Herd immunity has to be linked to the exact pathogen, cell, molecule or population process involved.
- The biological effect of herd immunity depends on the sequence from trigger to protective outcome.
- Clear distinctions within herd immunity prevent confusion with neighbouring immune responses.
- Evidence for herd immunity is strongest when mechanism and consequence are explained together.
ConceptIB Biology HL