A Large Vaccine-Derived Poliovirus Outbreak

(See the editorial commentary by Wright and Modlin, on pages 335–6.) Between June and October 2005, 45 laboratory-confirmed type 1 vaccine–derived poliovirus (VDPV) cases were identified onMadura Island in Indonesia. Genetic sequencing data on VDPV isolates were consistent with repli-cation and circulation for up to 2 years. Concurrent circulation with type 1 wild poliovirus (WPV) enabled comparisons of VDPV andWPV cases and found that clinical and epidemiological features of both were similar. Attack rates forVDPVwere ashigh as those forWPV.Of 41VDPVcasepatientswithknownvaccination status, 25 (61%) had received zero oral polio vaccine (OPV) doses. Low population immunity due to low routine OPV coverage in rural areas and the absence of WPV circulation for more than a decade were major predisposing factors for the emergence of VDPV. Suboptimal surveillance and a limited initial immunization response may have contributed to widespread circulation. Sensitive surveillance and prompt high-quality immunization re-sponses are recommended to prevent the spread of VDPVs. Trivalent oral polio vaccine (tOPV), a live vaccine con-sisting of Sabin attenuated poliovirus strains 1, 2 and 3, is the primary tool for the global eradication of poliovi-rus. OPV prevents paralytic disease through stimulatio