New research helps explain polio's persistence in India despite massive immunization efforts and offers hope for the campaign to stamp out the virus once and for all. The study, whose authors include some of the experts heading the global polio eradication effort, appears in the 17 November issue of the journal Science, published by AAAS, the nonprofit science society.

Polio is a highly infectious disease that primarily affects children under three years of age. Paralysis develops in a small minority of polio cases but is permanent and can be fatal.

Nicholas Grassly of Imperial College London and his colleagues analyzed reports of children with paralysis in India, collected since 1997, and used a computer model to determine which conditions most strongly influence the persistence of polio in the country.

In the impoverished states of Uttar Pradesh and Bihar, where India's recent polio epidemics originate, poor sanitation and high population density are the key obstacles to eradicating the virus, the researchers report. These conditions pack a one-two punch: they make it easier for the poliovirus to spread, and they decrease the efficacy of the vaccine.

In place of the standard, "trivalent" form of the vaccine, which contains weakened versions of each of the three types of poliovirus, using the strain-specific "monovalent" vaccine should compensate for these obstacles and boost the vaccine's efficacy to the point
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Contact: Natasha Pinol
npinol@aaas.org
202-326-7088
American Association for the Advancement of Science
16-Nov-2006