Measles is an infectious disease caused by a virus. The graph shows the number of cases of measles each year in a country before and after a vaccine was introduced. [Figure 40.1] What could have caused the decrease in the number of cases of measles after vaccination was introduced?
✓ Correct Answer
The correct answer is A: vaccines provided artificial active immunity in people: ✓, vaccines provided artificial passive immunity in people: X, fewer people are able to act as hosts for the virus: ✓
📋 Examiner Report & Trap Analysis
Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
🎯 Mark Scheme Breakdown
Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.
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