Journal of Infectious Diseases
Volume 203 Issue 7 April 1, 2011
http://www.journals.uchicago.edu/toc/jid/current

MAJOR ARTICLES AND BRIEF REPORTS
VIRUSES
Steven Wassilak, Muhammad Ali Pate, Kathleen Wannemuehler, Julie Jenks, Cara Burns, Paul Chenoweth, Emmanuel Ade Abanida, Festus Adu, Marycelin Baba, Alex Gasasira, Jane Iber, Pascal Mkanda, A. J. Williams, Jing Shaw, Mark Pallansch, and Olen Kew
editor’s choice: Outbreak of Type 2 Vaccine-Derived Poliovirus in Nigeria: Emergence and Widespread Circulation in an Underimmunized Population
J Infect Dis. (2011) 203(7): 898-909 doi:10.1093/infdis/jiq140

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Wild poliovirus has remained endemic in northern Nigeria because of low coverage achieved in the routine immunization program and in supplementary immunization activities (SIAs). An outbreak of infection involving 315 cases of type 2 circulating vaccine-derived poliovirus (cVDPV2; >1% divergent from Sabin 2) occurred during July 2005–June 2010, a period when 23 of 34 SIAs used monovalent or bivalent oral poliovirus vaccine (OPV) lacking Sabin 2. In addition, 21 “pre-VDPV2” (0.5%–1.0% divergent) cases occurred during this period. Both cVDPV and pre-VDPV cases were clinically indistinguishable from cases due to wild poliovirus. The monthly incidence of cases increased sharply in early 2009, as more children aged without trivalent OPV SIAs. Cumulative state incidence of pre-VDPV2/cVDPV2 was correlated with low childhood immunization against poliovirus type 2 assessed by various means. Strengthened routine immunization programs in countries with suboptimal coverage and balanced use of OPV formulations in SIAs are necessary to minimize risks of VDPV emergence and circulation.