The Eradication of Polio — Progress and Challenges
Mark A. Pallansch, Ph.D., and Hardeep S. Sandhu, M.D.
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Because of persistent viral transmission, polio eradication activities have been intensified in India, and most children in the northern part of the country are now receiving more than 12 doses of vaccine before their second birthday (many more than the number of doses that are recommended for routine vaccinations, but necessary to attain immunity in high-risk areas and to eradicate the virus in some populations). These increased activities have led to fatigue among both the local vaccination teams and the community members who participate. Moreover, a median of 10 reported vaccine doses have been received by persons who have contracted poliomyelitis; this has raised questions about the efficacy of the vaccine. The quality and potency of the vaccine have been tested and shown to be adequate, but various biologic and ecologic factors such as other enteric infections and poor nutrition may be contributing to its reduced effectiveness in inducing immunity in these particular reservoir populations. A perplexing discrepancy remains, however, since other areas of southern Asia — including other parts of India — have similar risk factors for the transmission of the virus because of poor sanitation and crowding and yet are now polio-free.
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