Mechanism of Action

The oral poliovirus vaccine stimulates the immune system to produce anti-poliovirus antibodies against Sabin poliovirus types 1, 2, and 3. The live virus persists in the gastrointestinal tract for 4-6 weeks, inducing both mucosal and serum anti-poliovirus antibodies capable of opsonization, neutralization, and complement activation. It is likely that reinfection with naturally occurring poliovirus or vaccine strains reinforces OPV-induced humoral immunity.

Pharmacokinetics

Antibody stimulation after oral administration of OPV occurs within 7-10 days and peaks at approximately 3 weeks. Poliovirus antibodies are distributed into breast milk. It is unknown if poliovirus antibodies cross the placenta (see CONTRAINDICATIONS). Most individuals are protected after one dose, and the majority of vaccinees are protected after two doses. The duration of immunity is not known, but studies in children have revealed that 95% of vaccinees have protective antibodies to all three virus types 5 years after vaccination.

Several studies suggest that intestinal resistance can persist for 6 years after vaccination.

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