Vaccine-derived poliovirus type 2 (VDPV2) detected in environmental samples in London

22 June 2022

The Global Polio Laboratory Network (GPLN) has confirmed the isolation of type 2 vaccine-derived poliovirus (VDPV2) from environmental samples in London, United Kingdom (UK), which were detected as part of ongoing disease surveillance.  It is important to note that the virus has been isolated from environmental samples only – no associated cases of paralysis have been detected.  Recent coverage for the primary course of DTaP/IPV/Hib/HepB vaccination, which protects against several diseases including polio, in London suggests immunization coverage of 86.6%.

Initially, vaccine-like type 2 poliovirus (SL2) had been isolated from samples taken from the same site between February and May 2022. Genetic analysis suggests that the new VDPV2 and previous SL2 isolates have a common origin, still to be identified, but the technical definition and criteria for ‘circulation’ of VDPV2 are not met at this time.  Additional sewage samples collected upstream from the main waste-water treatment plant’s inlet are being analysed.

Investigations and response by the UK Health Security Agency are ongoing  to:

  • assess both origin and risk of circulation associated with these isolates;
  • strengthen poliovirus surveillance including enterovirus and environmental;
  • explore routine immunization catch-up of children who are under-immunized, including of families that have recently arrived in the UK from countries with recent use of type 2-containing oral polio vaccine; and,
  • enhance communications about this incident to health professionals and caregivers.

It is important that all countries, in particular those with a high volume of travel and contact with polio-affected countries and areas, strengthen surveillance in order to rapidly detect any new virus importation and to facilitate a rapid response. Countries, territories, and areas should also maintain uniformly high routine immunization coverage at the district level and at the lowest administrative level to protect children from polio and to minimize the consequences of any new virus being introduced.

Any form of poliovirus anywhere is a threat to children everywhere. It is critical that the GPEI Polio Eradication Strategy 2022-2026 is fully resourced and fully implemented everywhere, to ensure a world free of all forms of poliovirus can be attained.


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