This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Types of vaccines, Subject name: Pediatrics
[{'content': "Mass vaccination is ineffective in inducing 'herd immunity' for: \nSelect and explain. \nA. Measles, B. Poliomyelitis, C. Tetanus, D. None of the above", 'role': 'user'}, {'content': 'Answer: C \nExplanation: Herd Immunity: -Reduction of infection / disease in unimmunized segment as a result of immunizing a propoion of population. - It is d/t reduced carriage of the causative microorganism by the vaccinated coho - Thus, seen only with vaccines against those diseases where humans are the only source -An effective vaccine is prerequisite for good herd effect. e.g. conjugated pneumococcal vaccine - Tetanus & BCG vaccines have no herd effect. So, mass vaccination is ineffective.', 'role': 'assistant'}]