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: Social & Preventive Medicine
Oral cholera vaccine is effective for: September 2005 
Select and explain. 
A. 6 months, B. 12 months, C. 2 years, D. 3 years
D: 3 years
Answer: D: 3 years 
Explanation: Ans. D: 3 years Oral vaccine is effective for at least 3 years. Injectable vaccine is effective for 3-6 months and protective value is about 50%. Proguanil and antibiotics should be avoided from one week before and one week after the administration of the live oral attenuated vaccine