Progress toward poliomyelitis eradication--India, January 2006-September 2007.

India is one of four countries where wild poliovirus (WPV) transmission has never been interrupted (the others are Afghanistan, Nigeria, and Pakistan). An outbreak of poliomyelitis cases caused by WPV type 1 (WPV1) occurred in India in 2006, primarily in the northern states of Uttar Pradesh and Bihar, where polio remains endemic. This outbreak resulted in the greatest annual number of cases of poliomyelitis in India since 2002. In response, the Government of India and its partners implemented additional vaccination measures based on recommendations from the India Expert Advisory Group on Polio Eradication. These measures focused predominantly on use of monovalent oral poliovirus vaccine type 1 (mOPV1), which has higher efficacy against WPV1 than trivalent OPV (tOPV). As a result, WPV1 cases in India decreased approximately 84% to 66 cases during January-September 2007, compared with 405 cases during the corresponding period in 2006. In western Uttar Pradesh, a state in which multiple risk factors have made interruption of WPV transmission challenging, five WPV1 cases have been reported this year, compared with 299 during the same period in 2006. However, a WPV type 3 (WPV3) outbreak also has been reported, with 261 cases occurring through September 30, 2007, primarily in the northern states where polio remains endemic. This report summarizes progress toward polio eradication in India during January 2006-September 2007 and highlights the challenges and strategic adaptations of eradication measures.