OPV mass vaccination campaigns impact transmission by which effect?

• A. Increase immunity only in vaccinated individuals
• B. Rapidly interrupt person-to-person transmission
• C. Permanently eradicate poliovirus after one campaign
• D. Have no effect on community transmission

Answer: (B)

Mass OPV campaigns reduce transmission by boosting gut mucosal immunity across a large portion of the population. Poliovirus replicates in the intestinal tract and is shed in stool, so strong intestinal immunity lowers viral replication and shedding. With fewer contagious people, transmission chains are interrupted quickly, making the campaign effective at rapidly stopping person-to-person spread. Immunity in vaccinated individuals is important, but the key is the population-wide interruption of transmission, not just individual protection. A single campaign won’t permanently eradicate poliovirus, and there is a real effect on community transmission rather than none.