What is the effect of OPV mass vaccination campaigns on wild poliovirus transmission?

• A. It has no effect on transmission.
• B. It can rapidly interrupt person-to-person transmission.
• C. It prolongs transmission chains.
• D. It increases the risk of outbreaks due to importations.

Answer: (B)

The main idea is that mass campaigns with the oral polio vaccine quickly stops the spread of wild poliovirus by boosting mucosal immunity across the community. OPV induces strong gut immunity, which reduces intestinal replication and viral shedding if infection occurs. When a large portion of the population is immunized in a short time, the number of susceptible people falls rapidly and transmission between people declines, often halting transmission chains in a matter of weeks to months. This is why such campaigns are effective at interrupting spread. While there are separate considerations about vaccine-derived poliovirus risk, the impact on wild poliovirus transmission from mass OPV campaigns is best described as rapid interruption of transmission, not a prolongation or no effect.