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': 'Which of the following is not a type of Vaccine derived polio virus? \nSelect and explain. \nA. cVDPV, B. iVDPV, C. mVDPV, D. aVDPV', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Vaccine derived polio virus (VDPV)\n\nProperties of VDPV:\n\n– Occurs due to Sabin (OPV) vaccine: P3 (60% of all cases) > P2 > P1\n– Clinical presentation indistinguishable from Wild polio virus (WPV)\n– cVDPV present similar public health threat like WPV\n– iVDPV prolonged infection may transmit virus to others\n\nIncidence of VDPV: 4 cases per million birth cohort per year\nTypes of VDPV:\n\n– cVDPV: Person-to-person transmission in community\n– iVDPV: Isolates from immunodeficient persons\n– aVDPV: Ambiguous from healthy person or sewage isolates\n\nKey risk factors for cVDPV emergence:\n\n– Development of immunity gaps (due to low OPV coverage)\n– Prior elimination of WPV types\n– Low routine immunization coverage with trivalent OPV\n– Insensitive AFP surveillance\n\nDiagnosis:\n\n– Real time Reverse transcription\n– PCR nucleic acid amplification', 'role': 'assistant'}]