Recent reports of poliovirus detected in samples from a sewage treatment works in London have rightly generated significant concern among public health agencies and medical staff. The poliovirus detected is what is called vaccine-derived poliovirus – this is not “wild poliovirus”.
There are currently two poliovirus vaccines: the oral poliovirus vaccine (OPV) and the inactivated poliovirus vaccine (IPV). Vaccine-derived poliovirus is linked to the use of the OPV as this vaccine uses weakened poliovirus to produce an immune response.
The weakened poliovirus can still infect people and be shed by the vaccinated person. This can result in the weakened virus spreading from person to person. And in rare cases, this weakened poliovirus can change to a more dangerous strain of the virus that can cause disease.
