The secondary attack rate (SAR) of measles in susceptible household contacts is approximately:

• A 20–30%
• B 50–60%
• C 40–50%
• D 75–90% ✓

Explanation

Measles has one of the highest secondary attack rates among respiratory infections, approximately 75–90% in unvaccinated susceptible household contacts, reflecting the basic reproductive number (R0) of 12–18. This extreme transmissibility underpins the need for ≥95% population immunity to achieve herd protection — the threshold for measles elimination.

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.