Transmission of wild poliovirus continues in four countries: Afghanistan, India, Nigeria, and Pakistan. From January 2006 to February 2007, the number of polio cases increased in Pakistan and Afghanistan. Poliovirus continues to circulate in these countries because insufficent numbers of infants receive three doses of oral polio vaccine – 69% and 64% in Afghanistan and Pakistan, respectively. More importantly, coverage varies significantly within the countries, with higher rates in areas with good health infrastructure, easy access, and high literacy.
To eradicate poliovirus from these countries, it will be necessary to overcome a very large challenge: to access and vaccinate children along the large border between the two countries that is remote and insecure. This border area is the main virus reservoir in the region and, because of frequent border crossings, is a principal source of poliovirus spread into other areas.
This problem illustrates the sad reality that control of disease depends not only upon good science – developing an effective vaccine – but also social, cultural, and political issues well beyond the knowledge of most scientists. Immunization truly spans multiple disciplines.
For more information, see MMWR.