Introduction
acute flaccid paralysis, poliomyelitis, vaccine-associated paralytic
POLIOMYELITIS, POLIO
Although live oral poliovirus vaccines (OPVs) are safe and effective and have led to the elimination of poliomyelitis from most of the world, in rare circumstances the attenuated viruses in OPVs can mutate and reacquire neurovirulence. This mutation can result in vaccine-associated paralytic polio in vaccine recipients and susceptible close contacts and, in settings of persistently poor immunisation coverage, can lead to the emergence of circulating vaccine-derived polioviruses (cVDPVs).However, despite the switch and cessation of routine use of live type 2 OPVs (OPV2), type 2 cVDPV (cVDPV2) outbreaks have occurred in many countries, resulting in cases of acute flaccid paralysis, which represent the majority of such polio cases worldwide.
