The polio endgame is proving to be challenging. On June 29, 28 children in the Democratic Republic of the Congo (DRC) were paralysed by the circulating vaccine-derived polio virus Type 2 (cVDPV). The World Health Organisation (WHO) has assessed the overall public health risk at the “national level to be very high and the risk of international spread to be high”. According to the WHO, there is an increased risk of virus transmission during the imminent rainy season. Thanks to intensified immunisation using oral polio vaccination (OPV), polio cases caused by the wild virus have reduced by 99.9% since 1988. However, as live, weakened viruses are used in OPV, there is a remote possibility of the virus turning virulent and causing vaccine-derived polio virus outbreaks. This is best seen in the case of Type 2 polio virus.
The only way to stop the outbreaks is by using OPV containing only Type 2. While the renewed use of Type 2 OPV raises the risk of further shedding of Type 2 viruses, using the polio vaccine injection (which uses only killed viruses) is not recommended during an outbreak as it takes longer to protect vaccinated children.