If the basic reproduction number (R0) of a highly contagious disease is 4, what is the minimum proportion of the population that must be immune to achieve herd immunity?
- A 50%
- B 60%
- C 75% ✓
- D 90%
Correct answer: C. 75%
Explanation
The herd immunity threshold is calculated using the formula 1 minus 1 divided by R0. For an R0 of 4, the threshold is 1 minus 1/4, which equals 1 minus 0.25, or 0.75. Therefore, at least 75 percent of the population must be immune to interrupt transmission and protect susceptible individuals. This concept is fundamental in vaccination programme planning.
Reference: Park's Textbook of Preventive and Social Medicine, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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