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To date, the world has seen eight outbreaks of circulating vaccine derived poliovirus, cVDPV, in Hispaniola, Indonesia, Egypt, Madagascar (×2), Philippines, China and Cambodia. This includes the very large Egyptian outbreak, from 1988 to 1993, an outbreak confirmed years later by retrospective examination of lab samples originally mistaken for wild poliovirus. As of this writing, January 2009, Nigeria is home to an outbreak of Type 2 VDPV that has continued for more than a year.
In this article from PLOS, Wringe and colleagues review the virological and epidemiological evidence on VDPV with special attention to case to infection ratios, paying particular attention to the large VDPV epidemics in Hispaniola, Indonesia and Egypt.
Wringe and colleagues do not minimize the importance of VDPV:
'To describe the problem of vaccine-derived polio as 114
virologically-confirmed cases, worldwide, over some twenty years,
gives a very different impression than a description which suggests a
minimum of hundreds of thousands, and more likely several million
infections by vaccine-derived viruses, some of which became endemic
in large populations. It is also possible that other vaccine-derived
virus lineages have circulated for limited time periods, but failed
to cause any clinical cases and were thus unrecognized[61]. The risk
of VDPV appearance and the incidence and spread of these infections
will be important considerations for policies relating to the
cessation of OPV, for future surveillance needs, and for planning for
outbreak control in the future, including stockpiling vaccines.'
These findings have important implications for the future of polio vaccination policy. One solution to VDPV is stockpiling of monovalent OPV. But is the solution a problem if mOPV runs the risk of generating fresh VDPV? Can we eliminate the risk of VDPV without recourse to IPV?
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