Compare OPV and IPV in terms of immunity: mucosal vs systemic, and risks.

• A. OPV induces systemic immunity with no mucosal effects; IPV induces mucosal immunity and can cause VAPP.
• B. OPV induces mucosal (intestinal) immunity and systemic immunity; it can rarely cause VAPP and can revert to cVDPV; IPV induces systemic humoral immunity with no fecal shedding risk and no VAPP risk but weaker mucosal immunity.
• C. OPV induces only mucosal immunity and has no risk of VAPP; IPV induces mucosal immunity.
• D. OPV induces only humoral immunity; IPV induces only mucosal immunity.

Answer: (B)