Inactivated Polio Vaccine: Its proposed role in the final stages of polio eradication

In 2000, the island of Hispaniola, home to Haiti and the Dominican Republic, was the first place where the existence of circulating vaccine derived poliovirus (cVDPV) was demonstrated [1]. As a live product, oral polio vaccine (OPV), once excreted, could enter the environment, reassort with other enteroviruses, and produce cVDPV [2]. After the investigation of that outbreak, the first of a dozen in the current century, a review of laboratory samples from elsewhere showed that other cVDPV had circulated in countries, notably Egypt [3], and was misclassified as wild poliovirus (WPV) at the time. It was recognized that the extent of cVDPV was large enough to pose a threat to the global eradication programme. In the current century, cVDPV has been found in countries as diverse as China and Madagascar, with three recent cases seen in Kenya, genetically linked to Somalia. A 2008 review of the first eight documented outbreaks, all from countries with poor OPV vaccination coverage, was not reassuring.