A 6-week-old infant receives the first dose of oral poliovirus vaccine (OPV). Two weeks later, the infant develops acute flaccid paralysis. Stool viral culture isolates a type 2 poliovirus. Which phenomenon explains this complication?

• A Natural poliovirus infection acquired independently
• B Vaccine failure due to maternal antibody interference
• C Cross-reaction with coxsackievirus in the OPV formulation
• D Vaccine-derived poliovirus (VDPV) reversion to neurovirulence ✓

Explanation

Vaccine-associated paralytic poliomyelitis (VAPP) and circulating vaccine-derived poliovirus (cVDPV) are known rare complications of OPV. The Sabin strains in OPV can undergo genetic reversion to neurovirulence, particularly type 2. This is why bivalent OPV (bOPV, covering types 1 and 3) replaced trivalent OPV globally in 2016, as type 2 wild poliovirus was eradicated. India switched to IPV for primary immunization to prevent VAPP, using OPV as a booster for intestinal immunity.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.