According to the World Health Organisation (WHO), Vaccine-derived poliovirus is a well-documented strain of poliovirus mutated from the strain originally contained in oral polio vaccine (OPV).
OPV contains a live, weakened form of poliovirus that replicates in the intestine for a limited period, thereby developing immunity by building up antibodies.
The virus is transmitted by person-to-person, mainly through the fecal-oral route or, less frequently, by a common vehicle (contaminated water or food) and multiplies in the intestine, from where it can invade the nervous system and cause paralysis.
