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
Which is the following is/are subunit vaccines 
Select and explain. 
A. Typhoid Vi, B. H. Influevza vaccine (Hib), C. Hepatitis B Vaccine, D. Diphtheria
A: Typhoid Vi
Answer: A: Typhoid Vi 
Explanation: This subunit vaccine is composed of purified VI capsular polysaccharide from the Ty2 S. Subcutaneously or intramuscularly. Stable for 6 months Only 1 dose is required and vaccine confers protection 7 days after injection. (refer pgno:237 park 23 rd edition)