One of the first applications of the Emergency Use Listing (EUL) procedure was the assessment of the novel oral polio vaccine type 2 (nOPV2), for which WHO developed a roadmap. nOPV2 is expected to become a key tool in addressing type-2 vaccine-derived polio and could significantly enhance progress in polio eradication.

Type 2 vaccine-derived polio is currently affecting a number of countries, notably in Africa, and also in some parts of the Middle East and Asia (including Pakistan, the Philippines and Somalia). Over the past five years, 423 cases have been detected in 19 countries. This occurs when routine immunization coverage is low or when supplementary immunization activities are poorly conducted and not enough children are reached with the vaccine. As a result, a population is left under-immunized and the vaccine virus is able to circulate among unvaccinated children and undergo genetic changes. Hence, the main risk factor is low vaccination coverage. A fully immunized population is protected against both vaccine-derived and wild polioviruses.

One of the key actions to address the current vaccine-derived polio emergency is to roll out nOPV2.