This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
Xavier and yogender stayed in the same hostel of the same university. Xavier develops an infection due to group B meningococcus. After few days yogender develops an infection due to Group C meningococcus. All of the following are true statements except 
Select and explain. 
A. Educate students about meningococcal transmission and take preventive measures, B. Chemoprophylaxis to all againts both group B and group C, C. Vaccine prophylaxis of contacts of xavier, D. Vaccine prophylaxis of contacts of yogendra
C: Vaccine prophylaxis of contacts of xavier
Answer: C: Vaccine prophylaxis of contacts of xavier 
Explanation: Monovalent and polyvalent vaccines containing the capsular polysaccharides of groups A, C, W-135 and Y are available. The vaccine induces good immunity after a single dose in older children and adults but is of little value in children below 2 years of age as the polysaccharide antigen is T-cell independent. Immunity is group specific. There is no group B vaccine available at present. Conjugate vaccine is now available, where the polysaccharide antigen conjugated to the diphtheria toxoid which makes the vaccine immunogenic for children below the age of 2 years. Reference: Textbook of Microbiology; Anathanarayan and panicker's; 10th edition; Page no: 233