How does OPV shedding influence vaccination program surveillance?

• A. Shed vaccine strains can be detected in stool and environmental samples; requires assays to differentiate vaccine strain from wild-type or cVDPV
• B. It has no impact on surveillance
• C. It prevents detection
• D. Shed vaccine strains can be detected in stool and environmental samples; requires assays to differentiate vaccine strain from wild-type or cVDPV

Answer: (D)

OPV shedding creates a detectable signal for poliovirus circulation because the live attenuated virus in the oral vaccine replicates in the gut and is excreted in stool and can be found in environmental samples like sewage. This enables vaccination programs to monitor poliovirus activity even when clinical cases are rare, providing a valuable supplement to clinical surveillance. The crucial point is that the material detected could be the vaccine strain, a wild-type strain, or a circulating vaccine-derived poliovirus, so laboratories must use molecular assays to differentiate the vaccine-derived strain from wild-type or cVDPV. Without this differentiation, positive detections could be misinterpreted. Thus, shedding allows surveillance through stool and environmental samples, but accurate interpretation depends on distinguishing vaccine strains from other poliovirus types.