This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Skin
What is the ideal time for staing post-exposure prophylaxis with acyclovir in a person exposed to varicella? 
Select and explain. 
A. Immediately after exposure, B. 3rd day, C. 7-9 th day, D. 10-14 th day
C: 7-9 th day
Answer: C: 7-9 th day 
Explanation: Antiviral therapy for prophylaxis against varicella should be staed 7 days after the intense exposure, using acyclovir. Ref: Harrisons Principles of Internal Medicine, 18th edition, Page: 1466