Social & Preventive Medicine Out of 10 relatives exposed to a primary case, of measles, 6 developed measles. Secondary attack rate of measles ? A 10-Apr B 10-Jun C 6-Apr D 4-Jun 💡 Explanation Out of 10 relatives exposed to a primary case, of measles, 6 developed measles. Secondary attack rate of measles ? ✓ Correct Answer: B. 10-Jun