Every country that was using trivalent oral polio vaccine (OPV) (containing all three serotypes of poliovirus) has permanently withdrawn this vaccine and either replaced it with bivalent OPV – containing only types 1 and 3 – or moved to an immunization schedule with only the inactivated form of polio vaccine (IPV).

Wild poliovirus type 2 has not been circulating since 1999 and was declared eradicated in September 2015. Removal of this eradicated serotype from the vaccine will further reduce the rare risk that a type 2 vaccine-derived poliovirus will emerge. The type 2 component of trivalent OPV also interferes with the immune response to poliovirus types 1 and 3.

For more information about the Polio Eradication Plan on the who.int website