How does OPV reduce the spread of poliovirus in the intestines?

• A. By boosting systemic antibody levels in blood only
• B. By killing the virus in the gut before replication
• C. By inducing a local immune response that limits viral multiplication
• D. By preventing entry into the bloodstream

Answer: (C)

The key idea is that immunity in the gut matters most for stopping poliovirus spread. Oral polio vaccine is taken into the intestine, where it prompts a strong mucosal immune response, especially secretory IgA in the intestinal lining. This local immunity neutralizes the virus right where it tries to multiply, so polio doesn’t replicate as much in the gut. With less replication, less virus is shed in the stool, which reduces transmission to others. This is different from relying on antibodies in the blood, which don’t reach the gut in high enough concentrations to prevent intestinal replication. It isn’t about killing the virus before it can replicate, but about limiting replication through a robust mucosal immune response that curtails shedding and spread.