摘要
Background:Vaccine-derived poliovirus(VDPV)is a potential threat to polio eradication because they can reintroduce into the general population and cause paralytic polio outbreaks,a phenomenon that has recently emerged as a prominent public health concern at the end of global polio eradication.This study aimed to describe the epidemiology and genetic characteristics of the frst VDPV identifed from a patient with acute faccid paralysis(AFP),with four doses of inactivated polio vaccine immunization in Henan Province,China in 2017.Methods:The patient was diagnosed with type 3 VDPV.Subsequently,a series of epidemiological approaches was implemented,including a retrospective search of AFP cases,rate of vaccination assessment,study of contacts,and supplementary immunization activities.Fecal samples were collected,viral isolation was performed,and the viral isolates were characterized using full-length genomic sequencing and bioinformatic analysis.Results:Phylogenetic analysis showed that the viral isolates from the patient were diferent from other reported genetic clusters of type 3 VDPV worldwide.They were identifed as a Sabin 3/Sabin 1 recombinant VDPV with a crossover site in the P2 region.Nucleotide substitutions,including U→C(472)and C→U(2493),have been identifed,both of which are frequently observed as reversion mutations in neurovirulent type 3 poliovirus.A unique aspect of this case is that the patient had been vaccinated with four doses of inactive polio vaccine,and the serum neutralizing antibody for Sabin types 1 and 3 were 1∶16 and 1∶512,respectively.Thus,the patient was speculated to have been infected with type 3 VDPV,and the virus continued to replicate and be excreted for at least 41 d.Conclusions:The existence of this kind of virus in human population is a serious risk and poses a severe challenge in maintaining a polio-free status in China.To the best of our knowledge,this is the frst report of VDPV identifed in the Henan province of China.Our results highlight the importance of maintaining a high-level vaccination rate and highly sensitive AFP case surveillance system in intercepting VDPV transmission.
