This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
Vaccine which requires most stringent condition for storage- 
Select and explain. 
A. DPT, B. OPV, C. BCG, D. TT
B: OPV
Answer: B: OPV 
Explanation: .oral polio vaccine is highly sensitive to varying temperatures.the cold chain temperature for storage of OPV are, routine storage at 2 to 8 degrees long term storage at -20 to-40 degrees ref:park&;s textbook,ed 22,pg no 138