Circulating vaccine-derived poliovirus and its implications for polio surveillance and eradication in Nigeria: A review of the literature

This review reports on circulating vaccine-derived poliovirus (cVDPV) and its implications for polio surveillance and eradication in Nigeria, a review of the literature. It also describes the potential implications of VDPVs in the final stages of global polio eradication. As the global eradication of wild poliovirus nears, the world health organization (WHO) is addressing challenges unprecedented cVDPV in public health. A circulating vaccine-derived poliovirus is a strain of poliovirus, genetically changed from its original strain contained in oral polio vaccine (OPV) and is an indication that far too many children remain unvaccinated or under-immunized. cVDPVs are not a new phenomenon only that poliomyelitis cases due to VDPVs are generally rare and have occurred in various parts of the world. The emergence of a vaccine-derived poliovirus that can circulate in the population shows that too many children remain under-immunized. Nigeria indeed is fighting an unusual outbreak of polio caused by mutating polio vaccine; the only remedy is to keep vaccinating children. cVDPVs in the past have been rapidly stopped with 2 - 3 rounds of high-quality immunization campaigns with OPV. The ongoing outbreak in 18 northern states of Nigeria’s 36 states is only appearing in areas where people are refusing to be vaccinated or where there is not enough oral polio vaccine (OPV). Recent outbreak of cVDPV in Nigeria has implications for the Global Polio Laboratory Network (GPLN) procedure for VDPV detection. It is an indication that far too many children remain unvaccinated or under-immunized. It also reaffirms that not enough children are protected from poliovirus (wild or vaccine-derived) and that much more must be done to reach all children with vaccine. This resurgence of polio by international spread is also a setback to the Global Polio Eradication Initiative that had successfully decreased the number of polio-affected countries to only 9 in 2002. All countries are at risk until polio has been completely eradicated. The solution is the same for all polio outbreaks: immunize every child several times with OPV to stop polio transmission, regardless as to the origin. One strategy to protect polio-free countries from reintroduction of wild poliovirus is by requiring proof of polio vaccination for all incoming travelers from polio-endemic countries. Heightened immunization campaign for children was a necessity to stop the endemic from spreading. In conclusion, in all other countries with ongoing WPV or VDPV transmission, serious limitations in accessing and vaccinating children remain the major impediments to polio eradication. In Nigeria, the key to success will be to scale-up throughout the country the communication, social mobilization, and operational improvements that were achieved in some areas of northern Nigeria. The best way to overcome the outbreak of vaccine-related polio virus will be to increase immunization coverage, making sure that all children get the vaccine.   Key words: Polio eradication, poliovirus, poliomyelitis, vaccination, circulating vaccine derived poliovirus (VDPV).