CDC: leading research for pre- and post-eradication issue
The US Centers for Disease Control and Prevention (CDC) is performing and collaborating on various polio eradication research projects which are directed toward accelerating the interruption of wild poliovirus transmission as well as supporting the risk assessment and management for the post-eradication period.
Pre-eradication: supporting Nigeria and India’s eradication efforts
Because a high proportion of children in high-risk states of northern Nigeria continue to be unvaccinated against polio, a comprehensive risk factor assessment has been initiated in collaboration with the Ministry of Health’s National Primary Health Care Development Agency, the World Health Organization (WHO), UNICEF and other partners. This assessment will evaluate characteristics of the child who is unvaccinated and its family, in comparison with a child who is vaccinated. The assessment will further explore the comparative issues relating to immunization delivery in routine health services and supplementary immunization activities (SIAs) and community support. Initial results of this assessment are expected by end-2009.
In India, the wild poliovirus (WPV) case numbers are low and the geographic extent of transmission is limited. Interrupting the transmission of WPV simultaneously in the two remaining endemic states - Uttar Pradesh and Bihar - is key to ultimate success. To help achieve this, in addition to various research projects aimed at improving the effectiveness of polio vaccination, CDC - in joint collaboration with WHO’s National Polio Surveillance Project (NPSP) - has designed two projects to expand surveillance of WPV in high-risk areas of those two states to older age groups, including adults. The projects aims to find if faecal specimens (and pharyngeal swabs in some settings) from persons aged >five years in households and/or neighbourhoods of recent WPV cases suggest any participation of older aged individuals in WPV transmission. If substantial evidence is found and WPV transmission persists, this could inform a possible expansion of the target age group for SIAs in these areas. Initial results of this expanded age group surveillance are expected by September.
Post-eradication: helping gain crucial insight to secure a lasting polio-free world
Mexico in 2008 has switched polio vaccination policy to routine use of inactivated poliovirus vaccine (IPV) while continuing with twice annual campaigns with oral poliovirus vaccine (OPV). CDC, in collaboration with the Pan American Health Organization (PAHO), has initiated a project with the Ministry of Health’s Centro Nacional para la Salud de la Infancia y la Adolescencia in which sewage is sampled before, during and after OPV campaigns to determine the persistence of OPV virus excretion in the population in this setting and to follow this over time. The poliovirus national reference laboratory at the Instituto Nacional de Diagnóstico y Referencia Epidemiológicos will be conducting the testing. Preliminary results are expected in 2010.
The Global Polio Laboratory Network (GPLN) has continued to adopt new methodologies and approaches to improve the timeliness and accuracy of poliovirus detection from acute flaccid paralysis (AFP) specimens. This has been most evident in the development, evaluation and implementation of new molecular techniques using new algorithms to rapidly identify and characterize polioviruses. Using methods developed in the CDC polio laboratory based on real-time Reverse Transcriptase Polymerase Chain Reaction (RTPCR), it is now possible to replace previous methods with ones that are simpler, more reliable and can identify both wild polioviruses and vaccine-derived polioviruses (VDPVs) more quickly. The implementation of these methods is now in progress with joint CDC/WHO workshops conducted in two regions, with three more scheduled for late 2009. It is envisaged that these new methods will be introduced into all polio-endemic regions by end-2009.
In addition to developing laboratory methods to address current AFP surveillance activities, two projects are also in progress to address potential future polio surveillance systems. The first project focuses on the continued expansion of the use of molecular methods to replace time consuming and resource intensive steps in the process of poliovirus isolation. Current steps that are dependent on growing the virus in cell culture could be replaced by PCR methods that can directly detect the virus from the original faecal specimen, further improving the speed of polio detection. The second project will examine the use of immunological markers to look for evidence of poliovirus infection once polio has been eradicated and OPV immunization has ceased. This could greatly expand the ability to use simple ELISA tests to bring poliovirus diagnostics to many more sites and possibly integrate this laboratory testing with already existing measles laboratories that are performing similar tests.