Igcse Model Questions Vol1 2025 Biology Question 27

Practice objective / multiple choice question 27 from the 2025 Igcse Model Questions Vol1 Biology examination.

Igcse Model Questions Vol1 2025 Biology Objective / Multiple Choice Hard Difficulty
Question 27 IGCSE_MODEL_QUESTIONS_VOL1 • 2025 • BIOLOGY • objective

In a community of 10 000 people, 200 cases of disease X occurred in one year before a vaccine was introduced. After vaccination, 2 000 people were vaccinated and 30 cases occurred among them, while 8 000 unvaccinated people experienced 180 cases. (a) Calculate the vaccine efficacy using the formula \(\text{Efficacy}=\frac{\text{AR}_U-\text{AR}_V}{\text{AR}_U}\times100\), where \(\text{AR}_U\) and \(\text{AR}_V\) are the attack rates in unvaccinated and vaccinated groups respectively. (b) Assuming the entire community were vaccinated, estimate the expected number of cases in a year and state whether a public‑health target of fewer than 50 cases would be achieved.

Answer Options

Correct Answer A. Vaccine efficacy ≈ 33.3 %; expected cases if all vaccinated ≈ 150; target of < 50 cases not achieved.
B. Vaccine efficacy ≈ 40.0 %; expected cases if all vaccinated ≈ 120; target of < 50 cases not achieved.
C. Vaccine efficacy ≈ 33.3 %; expected cases if all vaccinated ≈ 80; target of < 50 cases not achieved.
D. Vaccine efficacy ≈ 33.3 %; expected cases if all vaccinated ≈ 150; target of < 50 cases achieved.
Correct Answer
A
Correct Option:
Vaccine efficacy ≈ 33.3 %; expected cases if all vaccinated ≈ 150; target of < 50 cases not achieved.

About This Question

This is Igcse Model Questions Vol1 2025 Biology Question 27. It is one of the objective questions from the 2025 Igcse Model Questions Vol1 Biology examination.

Difficulty level: Hard .

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