In the context of polio eradication, which of the following correctly describes the biological basis for Vaccine-Associated Paralytic Poliomyelitis (VAPP)?
- A OPV strains are inactivated viruses that revert to wild-type due to mutation
- B The attenuated OPV strains undergo reversion of neurovirulence through back-mutation in the gut, especially in immunodeficient individuals ✓
- C IPV strains cause VAPP through direct injection site neuropathy
- D VAPP is caused by contact with environmental poliovirus circulating in sewage
Correct answer: B. The attenuated OPV strains undergo reversion of neurovirulence through back-mutation in the gut, especially in immunodeficient individuals
Explanation
OPV contains live attenuated poliovirus strains. The attenuation is maintained by mutations in non-coding regions that reduce neurovirulence. After administration, these mutations can revert during viral replication in the gut, particularly in immunodeficient individuals. VAPP occurs at approximately 1 per 2.4 million doses, predominantly with the type 2 component, which is why bOPV (bivalent, containing types 1 and 3) replaced tOPV globally and IPV was introduced to cover type 2.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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