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: Microbiology
True regarding pertussis vaccine is - 
Select and explain. 
A. 95% of vaccinated are protected, B. Erythromycin should be given to contacts, C. Neuroparalytic Complication is seen in 1 in 15000, D. Leucocytosis is diagnostic
B: Erythromycin should be given to contacts
Answer: B: Erythromycin should be given to contacts 
Explanation: None