Progress toward poliomyelitis eradication--Pakistan and Afghanistan, 2007.

Of the four countries worldwide where wild poliovirus (WPV) transmission has never been interrupted, Pakistan and Afghanistan are considered a single epidemiologic block. Use of intense poliomyelitis eradication measures, including close coordination between the two countries and increased use of monovalent oral poliovirus vaccines (mOPVs) against type 1 WPV (WPV1) and type 3 WPV (WPV3), has reduced WPV transmission to historically low levels. However, despite these efforts, in 2007 both types of WPV continued to circulate in areas of Pakistan and Afghanistan. Ongoing conflicts and security concerns in remote areas with rugged terrain limit access to children and decrease vaccination coverage from routine and supplementary immunization activities (SIAs) in border areas of both countries where WPV transmission is endemic. In other WPV-endemic areas of Pakistan, where security and access concerns do not exist, operational problems in implementing SIAs resulted in inadequate vaccination of children, which failed to interrupt WPV transmission. This report updates previous reports and describes polio eradication activities in Pakistan and Afghanistan during January-December 2007 (data as of March 22, 2008). Further progress toward polio eradication will require continued measures to address security concerns in portions of both countries and problems with implementing SIAs in secure areas of Pakistan.