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
[{'content': 'True about measles outbreak ? \nSelect and explain. \nA. Occurs if propoion of susceptible children is >20%, B. Infects 50% children in virgin community, C. Vaccination given at 6 months, D. Every 6-7 years', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Vaccination given at 6 months Epidemic of measles occur if propoion of susceptible children is > 40%. If measles is introduced in a virgin community, it infects > 90% of children. Measles vaccine is given at the age of a months, but age can be lowered to 6 months in epidemics. Measles shows a cyclic trend with epidemic every 2-3 years.", 'role': 'assistant'}]