It is well recognised that the live, highly attenuated poliovirus strains (Sabin 1, 2, and 3) can mutate sufficiently to regain virulence and cause outbreaks of poliomyelitis. It is rare but tends to occur in settings of persistently low immunisation coverage, where extensive viral replication and person-to-person transmission are possible. On 22 June 2022, the UK Health Security Agency announced that vaccine-derived poliovirus type 2 (VDPV2) had been repeatedly detected in sewage in London, UK. This has demonstrated that vaccine-derived polioviruses (VDPVs) can emerge in high-income settings with good sanitation where the live oral polio vaccine (OPV) is not in use. Hill M et al. Lancet 2022;400:713-715 has summarised the evidence and controversy around this issue and merits a read. The multifactorial reasons for this event and others reported throughout the world, are discussed. Three urgent mandatory interventions are required: (1) poliovirus surveillance is needed in affected countries and more broadly in countries without any, (2) an urgent emphasis must be placed on improving vaccination coverage, (3) evaluation of interventions is needed to assess the extent to which improving coverage of the unvaccinated. Failure to get this right threatens the global progress towards polio eradication.
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