Which statement best contrasts immunity conferred by IPV and OPV?

• A. IPV produces mucosal intestinal immunity; OPV induces systemic humoral immunity.
• B. IPV produces systemic humoral immunity; OPV induces mucosal intestinal immunity and additional systemic immunity.
• C. Both vaccines induce only humoral immunity.
• D. Neither vaccine induces mucosal or systemic immunity.

Answer: (B)

The key idea is how each vaccine shapes the immune defense. Inactivated polio vaccine (IPV) is given by injection and mainly drives antibodies in the bloodstream—systemic humoral immunity. It neutralizes the virus in the blood and protects against paralytic disease, but it doesn’t reliably generate strong mucosal immunity in the gut, so intestinal infection and virus shedding can still occur after exposure.

Oral polio vaccine (OPV) is a live attenuated vaccine taken by mouth. It replicates in the gut lining, stimulating mucosal immunity there—primarily secretory IgA in the intestinal mucosa—which is crucial for blocking infection and transmission in the gut. At the same time, OPV also induces systemic immune responses, providing additional systemic immunity beyond the mucosa.

So the best contrast is that IPV produces systemic humoral immunity, whereas OPV induces mucosal intestinal immunity and also elicits systemic immunity.