Type 2 Poliovirus Detection after Global Withdrawal of Trivalent Oral Vaccine

New England Journal of Medicine
August 30, 2018  Vol. 379 No. 9
http://www.nejm.org/toc/nejm/medical-journal

Original Articles
Type 2 Poliovirus Detection after Global Withdrawal of Trivalent Oral Vaccine
Isobel M. Blake, Ph.D., Margarita Pons-Salort, Ph.D., Natalie A. Molodecky, Ph.D., Ousmane M. Diop, Ph.D., Paul Chenoweth, N.D., Ananda S. Bandyopadhyay, M.B., B.S., Michel Zaffran, Eng.,
Roland W. Sutter, M.D., and Nicholas C. Grassly, D.Phil.
Background
Mass campaigns with oral poliovirus vaccine (OPV) have brought the world close to the eradication of wild poliovirus. However, to complete eradication, OPV must itself be withdrawn to prevent outbreaks of vaccine-derived poliovirus (VDPV). Synchronized global withdrawal of OPV began with serotype 2 OPV (OPV2) in April 2016, which presented the first test of the feasibility of eradicating all polioviruses.
Methods
We analyzed global surveillance data on the detection of serotype 2 Sabin vaccine (Sabin-2) poliovirus and serotype 2 vaccine–derived poliovirus (VDPV2, defined as vaccine strains that are at least 0.6% divergent from Sabin-2 poliovirus in the viral protein 1 genomic region) in stool samples from 495,035 children with acute flaccid paralysis in 118 countries and in 8528 sewage samples from four countries at high risk for transmission; the samples were collected from January 1, 2013, through July 11, 2018. We used Bayesian spatiotemporal smoothing and logistic regression to identify and map risk factors for persistent detection of Sabin-2 poliovirus and VDPV2…
Conclusions
High population immunity has facilitated the decline in the prevalence of Sabin-2 poliovirus after OPV2 withdrawal and restricted the circulation of VDPV2 to areas known to be at high risk for transmission. The prevention of VDPV2 outbreaks in these known areas before the accumulation of substantial cohorts of children susceptible to type 2 poliovirus remains a high priority. (Funded by the Bill and Melinda Gates Foundation and the World Health Organization.)