This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable diseases, Subject name: Social & Preventive Medicine
All are true about measles except- 
Select and explain. 
A. Incubation period is 10-14 days, B. Secondary attack rate is 30-40%, C. Sub cutaneous vaccine is available, D. Vaccine is live attenuated
B: Secondary attack rate is 30-40%
Answer: B: Secondary attack rate is 30-40% 
Explanation: <p>MEASLES:- An acute highly infectious disease of childhood caused by a specific virus of group myxovirus. Clinically characterised by fever and catarrhal symptoms of the upper respiratory tract( coryza,cough), followed by a typical rash. Incubation period-10 days from exposure to onset of fever and 14 days of appearance of rash. Secondary attack rate-infection confers life long immunity as there is only one antigenic type. Vaccine- live attenuated subcutaneous vaccine. {Reference: park&;s textbook of preventive and social medicine, 23rd edition, pg no.149}</p>