To avoid the risks for vaccine-associated paralytic polio¹ and circulating vaccine-derived poliovirus (cVDPV) outbreaks,² the Polio Eradication and Endgame Strategic Plan³ 2013-2018 directs the phasing out of all oral poliovirus vaccine (OPV) use after wild poliovirus (WPV) is eradicated. This has started with the type 2 component in the vaccine. From April 17 through May 1, 2016, 155 countries using trivalent OPV (tOPV) (Sabin strains of types 1, 2, and 3) in their national immunization schedules removed it and introduced bivalent OPV (bOPV) (Sabin strains of types 1 and 3).³ This massive public health event required the engagement of every health facility providing vaccines in each of these countries. This unprecedented, synchronized vaccine introduction and withdrawal is termed the switch.^4,5