Waec Model Questions Vol1 2017 Biology Question 47

Practice objective / multiple choice question 47 from the 2017 Waec Model Questions Vol1 Biology examination.

Waec Model Questions Vol1 2017 Biology Objective / Multiple Choice Hard Difficulty
Question 47 WAEC_MODEL_QUESTIONS_VOL1 • 2017 • BIOLOGY • objective

For a contagious disease the basic reproduction number is R₀ = 2.5. A vaccine available is 80 % effective. (a) What minimum proportion of the population must be vaccinated to achieve herd immunity? (b) If only 60 % of the population is vaccinated, calculate the effective reproduction number Rₑ. (c) Starting from a single infected individual, estimate the total number of cases after three successive generations of transmission using Rₑ.

Answer Options

Correct Answer A. Minimum vaccination coverage = 75 %; Effective Rₑ with 60 % coverage = 1.3; Expected cases after three generations ≈ 6
B. Minimum vaccination coverage = 75 %; Effective Rₑ with 60 % coverage = 1.0; Expected cases after three generations ≈ 4
C. Minimum vaccination coverage = 70 %; Effective Rₑ with 60 % coverage = 1.3; Expected cases after three generations ≈ 5
D. Minimum vaccination coverage = 60 %; Effective Rₑ with 60 % coverage = 1.5; Expected cases after three generations ≈ 7
Correct Answer
A
Correct Option:
Minimum vaccination coverage = 75 %; Effective Rₑ with 60 % coverage = 1.3; Expected cases after three generations ≈ 6

About This Question

This is Waec Model Questions Vol1 2017 Biology Question 47. It is one of the objective questions from the 2017 Waec Model Questions Vol1 Biology examination.

Difficulty level: Hard .

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