Novel oral poliovirus vaccine type 2 is an important eradication tool, but reaching every last child remains vital

Novel oral polio vaccine type 2 (nOPV2) has been genetically engineered to reduce the reversion events that can occur with Sabin oral polio vaccine (OPV) and result in loss of attenuation. 1 Yeh MT Bujaki E Dolan PT et al. Engineering the live-attenuated polio vaccine to prevent reversion to virulence. Cell Host Microbe. 2020; 27 (51.e8): 736 Summary Full Text Full Text PDF PubMed Scopus (91) Google Scholar As population immunity fell following the global withdrawal of the type 2 Sabin OPV in April 2016, such reversions resulted in a rapid increase in cases of acute flaccid paralysis caused by type 2 vaccine-derived poliovirus. Monovalent Sabin OPV type 2 (mOPV2) was initially used to control outbreaks but drove further vaccine-derived polio cases. 2 Macklin GR O'Reilly KM Grassly NC et al. Evolving epidemiology of poliovirus serotype 2 following withdrawal of the serotype 2 oral poliovirus vaccine. Science. 2020; 368: 401-405 Crossref PubMed Scopus (75) Google Scholar The vicious cycle that ensued threatened to derail polio eradication efforts. Given this threat, and its declaration as a Public Health Emergency of International Concern in November 2020, nOPV2 became the first vaccine globally to receive Emergency Use Listing (EUL) from WHO. Listing was based on reassuring safety and immunogenicity data from early phase clinical trials. Effectiveness of poliovirus vaccines against circulating vaccine-derived type 2 poliomyelitis in Nigeria between 2017 and 2022: a case-control studyWe found no significant difference in estimated effectiveness of the two oral vaccines, supporting the recommendation that the more genetically stable nOPV2 should be preferred in cVDPV2 outbreak response. Our findings highlight the role of IPV and the necessity of strengthening routine immunisation, the primary route through which IPV is delivered. Full-Text PDF Open Access