Which statement is true about OPV and transmission compared with IPV?

• A. OPV reduces transmission less effectively than IPV.
• B. IPV produces systemic humoral immunity; OPV induces mucosal intestinal immunity and additional systemic immunity.
• C. OPV has no impact on transmission.
• D. IPV reduces transmission more than OPV.

Answer: (B)

The key idea is how the type of polio vaccine shapes where immunity is built and how that affects transmission. OPV, being a live attenuated vaccine given by mouth, stimulates strong mucosal immunity in the gut (primarily IgA) and also some systemic immunity. This mucosal defense limits viral replication and shedding in the intestines, which helps reduce person-to-person transmission. IPV, given by injection, mainly elicits systemic humoral immunity (IgG) that protects the vaccinated person from disease but does not induce strong mucosal immunity in the gut, so transmission is less effectively suppressed.

The statement reflects this difference in immune responses: IPV produces systemic humoral immunity; OPV induces mucosal intestinal immunity and additional systemic immunity. This combination explains why OPV is more effective at reducing transmission than IPV, while IPV still provides important protection against disease.