Example 1
Classify protection from a vaccine and from an injection of ready-made antibodies.
Vaccination is active immunity. Transferred antibodies give passive immunity.
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Year 11 · SACE Stage 1
Active, passive and vaccine immunity
Classify immunity mechanisms and calculate simple vaccine-data quantities.
Method and worked examples
Active immunity develops when an individual’s immune system responds to antigen exposure, including vaccination or infection. It can generate memory cells. Passive immunity transfers ready-made antibodies, for example from maternal sources or an antibody preparation. It can provide rapid protection, but transferred antibodies are gradually lost and do not themselves create the recipient’s antigen-specific memory.
Vaccines expose the immune system to antigen or instructions for making antigen without requiring the full disease process. Booster doses can strengthen or restore responses. When enough people are protected against infection or onward transmission, spread may be reduced, indirectly protecting some others. This effect depends on the pathogen and vaccine; no single coverage percentage guarantees control of every infectious disease.
Example 1
Example 2
Disease risks in a stated comparison are 10% without vaccination and 2% with vaccination. Calculate relative risk reduction.
1010−2×100=80%. This is relative reduction for the supplied data.
Watch out: Transferred antibodies provide temporary protection; they do not by themselves establish the recipient’s antigen-specific memory.