Mucosal Immunity after Vaccination with Monovalent and Trivalent Oral Poliovirus Vaccine in India

Background. Persistent wild-poliovirus transmission, particularly in India, has raised questions about the degree of mucosal immunity induced by oral poliovirus vaccine (OPV) in tropical countries. Methods. Excretion of vaccine poliovirus after challenge with OPV was measured in stool samples collected from children identified by the acute flaccid paralysis surveillance program in India during 2005-2007. The effectiveness of trivalent and monovalent OPV against excretion of each poliovirus type was estimated. Results. Vaccine poliovirus was isolated from 4994 (5.2%) of 96,641 children with 2 stool samples. The relative odds of excreting challenge poliovirus among children with >= 5 reported previous doses of trivalent OPV compared with 0 previous doses was 0.24 (95% confidence interval [CI], 0.12-0.45), 0.08 ( 95% CI, 0.04-0.14), and 0.40 ( 95% CI, 0.19-0.85) for serotypes 1, 2, and 3, respectively, but the relative odds increased to 0.62 ( 95% CI, 0.44-0.88), 0.44 ( 95% CI, 0.20-0.99), and 0.66 ( 95% CI, 0.41-1.06), respectively, in the northern states of Uttar Pradesh and Bihar. In these 2 states, the relative odds of excretion of serotype 1 was 0.32 ( 95% CI, 0.26-0.41) after >= 5 doses of type 1 monovalent OPV. Conclusions. The mucosal immunity induced by OPV in India varies by location, serotype, and vaccine formulation. These findings have implications for global eradication and the potential role played by inactivated vaccine in this setting.