Which vaccine induces intestinal immunity?

• A. Oral poliovirus vaccine (OPV)
• B. Inactivated poliovirus vaccine (IPV)
• C. Both OPV and IPV
• D. Neither OPV nor IPV

Answer: (A)

Intestinal mucosal immunity is driven by responses in the gut, especially secretory IgA, which can block poliovirus replication in the intestinal tract and reduce fecal shedding. The oral poliovirus vaccine is a live attenuated vaccine taken by mouth; it actively replicates in the gut and stimulates strong mucosal immunity, producing local IgA and memory in the intestinal lining. This direct gut involvement helps prevent intestinal infection and interrupts transmission. The inactivated poliovirus vaccine, given by injection, mainly induces systemic antibodies that protect against paralysis but do not reliably elicit mucosal immunity in the gut. Therefore, the vaccine that induces intestinal immunity is the oral poliovirus vaccine.