Community Medicine (PSM) · Screening of Diseases and Health Concepts

For an infectious disease with a basic reproduction number (R0) of 4, the herd immunity threshold is approximately:

A 90%
B 75% ✓
C 50%
D 25%

Correct answer: B. 75%

Explanation

Herd immunity threshold equals 1 minus 1 divided by R0. For R0 equals 4, HIT equals 1 minus 0.25, which is 0.75 or 75%. This means at least 75% of the population must be immune to interrupt sustained transmission. Higher R0 values require higher vaccination coverage to achieve herd protection.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.

Want to test yourself?

Create a free account for timed mock tests, mistake tracking, and FSRS spaced-repetition revision across 43,000+ MCQs.

Start free → Log in

More Screening of Diseases and Health Concepts MCQs

A screening test for cervical cancer (VIA) has a sensitivity of 80% and specificity of 85%. In a population with 5% prevalence of disease, what is the positive predictive value (PPV)?
Which of the following is a requirement for a disease to be suitable for population-based screening?
A screening test for diabetes has sensitivity 80% and specificity 90%. In a population with 10% diabetes prevalence, the Positive Predictive Value (PPV) is approximately:
When two screening tests are applied in PARALLEL (simultaneously) for the same disease, the result compared to using either test alone is:
A test has sensitivity 90% and specificity 85%. The Likelihood Ratio of a Positive test (LR+) is:
Wilson and Jungner (1968) proposed classic criteria for a screening programme. Which of the following is NOT among their original 10 criteria?
A new cancer screening test is evaluated in a population. The Likelihood Ratio Positive (LR+) is 15 and Likelihood Ratio Negative (LR−) is 0.04. Which interpretation is correct?
A screening test for cervical cancer has a sensitivity of 80% and specificity of 90%. In a population with a disease prevalence of 1%, the Positive Predictive Value (PPV) of the test is approximately:

See all Screening of Diseases and Health Concepts MCQs →