This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: general microbiology, Subject name: Microbiology
[{'content': 'The Haemophilus influenzae vaccine contains which of the following \nSelect and explain. \nA. Lipopolysaccharide (LPS), B. Live attenuated H. influenzae, C. Polypeptide antigens containing D-glutamate, D. Polyribitol phosphate antigens', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Polysaccharide vaccine Haemophilus influenzae type b is a bacterium with a polysaccharide capsule; the main component of this capsule is polyribosyl ribitol phosphate (PRP). Anti-PRP antibodies have a protective effect against Hib infections. Thus, purified PRP was considered a good candidate for a vaccine Ref ananthnarayana microbiology textbook 8/e', 'role': 'assistant'}]