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The feasibility of global polio eradication is being questioned as a result of continued transmission in a few localities that act as sources for outbreaks elsewhere. Perhaps the greatest challenge is in India, where transmission has persisted in Uttar Pradesh and Bihar despite high coverage with multiple doses of vaccine. We estimate key parameters governing the seasonal epidemics in these areas and show that high population density and poor sanitation cause persistence by not only facilitating transmission of poliovirus but also severely compromising the efficacy of the trivalent vaccine. We analyze strategies to counteract this and show that switching to monovalent vaccine may finally interrupt virus transmission.

Original publication




Journal article


Science (New York, N.Y.)

Publication Date





1150 - 1153


Department of Infectious Disease Epidemiology, Imperial College London, Norfolk Place, London, UK.


Humans, Poliomyelitis, Poliovirus Vaccine, Oral, Sanitation, Disease Outbreaks, Population Density, Dose-Response Relationship, Immunologic, Child, Immunization Programs, India