Cooper, L. V., Bandyopadhyay, A. S., Gumede, N., Mach, O., Mkanda, P., Ndoutabé, M., Okiror, S. O., Ramirez-Gonzalez, A., Touray, K., Wanyoike, S., Grassly, N. C., & Blake, I. M. (2022). risk factors for the spread of vaccine-derived type 2 polioviruses after global withdrawal of trivalent oral poliovirus vaccine and the effects of outbreak responses with monovalent vaccine: a retrospective analysis of surveillance data for 51 countries in Africa. Lancet infectious diseases, 22(2), 284–294. http://access.bl.uk/ark:/81055/vdc_100150526913.0x000011