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 of the following vaccines can be used: 
Select and explain. 
A. 1 and 2 alone, B. 1 alone, C. 3 and 4 alone, D. 2 alone
A: 1 and 2 alone
Answer: A: 1 and 2 alone 
Explanation: ANS. A