The 'Herd Immunity Threshold' (HIT) for measles, whose R₀ is approximately 12–18, is closest to:

• A 50%
• B 83–95% ✓
• C 70%
• D 99%

Explanation

HIT = 1 − (1/R₀). For measles R₀ of 12–18: HIT = 1 − 1/12 to 1 − 1/18 = 91.7%–94.4% ≈ 83–95%. This explains why measles requires >95% vaccination coverage for elimination — the highest HIT among common vaccine-preventable diseases. Measles outbreaks occur even when coverage exceeds 90%, highlighting the need for the two-dose MR schedule.

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.