London's Poliovirus Confirmations Continue Unabated
The U.K. Health Security Agency (UKHSA) recently announced it continues investigating the source of the poliovirus identified in wastewater systems across London, England.
The UKHSA stated on October 19, 2022, it is most likely that an individual entered the U.K. in February 2022 from a country where the oral polio vaccine (OPV) had been used for immunization campaigns.
Recently vaccinated individuals can shed the OPV virus in their stool for a few weeks following vaccination enabling the virus to be detected through sewage surveillance.
Vaccine-like type-2 poliovirus (PV2) isolates were found in sewage samples collected from the London Beckton sewage treatment works. This analysis has shown that all PV2 isolates identified since then are genetically related.
This is an important finding since the Beckton sewage treatment plant covers a large catchment area with a population of close to 4 million people across north-east and north-central London.
Based on this sampling, poliovirus is considered present in sub-areas of the Beckton plant covering all or parts of Barnet, Brent, Camden, Enfield, Hackney, Haringey, Islington, and Waltham Forest boroughs.
The wastewater sampling has also detected the virus in lower concentrations and frequency in areas adjacent to the Beckton catchment area to the South (below the Thames river) and to the East.
The level of PV2 found and the high genetic diversity among the PV2 isolates suggests poliovirus transmission in separate networks of individuals in these boroughs and possibly in some other surrounding areas.
The pattern is inconsistent with virus shedding by one or a few individuals.
The UKHSA stated on October 19, 2022, as expected, the poliovirus has evolved and has met the criteria of vaccine-derived poliovirus (VDPV2), which means that it has re-acquired the mutations that cause paralysis.
The high-density population in the areas affected and the number of individuals under-vaccinated in those London boroughs suggests significant potential for the VDPV2 to continue to spread.
This indicates that under-vaccinated children can become infected and pass the infection on to others.
UKHSA has recently declared a national enhanced incident response to coordinate the investigation and response to the polio incident.
In London, an active call-recall of unvaccinated and partially vaccinated children under five is already underway, with a planned phased extension up to 18-year-olds.
However, due to the large pool of partially vaccinated or unvaccinated individuals in the affected areas of London, it is doubtful that this IPV-catch-up alone will be sufficient to prevent cases of paralysis or control the VDPV2 spread.
But, the Joint Committee on Vaccination and Immunisation met over the summer and determined in addition to ongoing catch-up, a supplementary IPV booster campaign should be implemented for children aged 1 to 9 years old living in London.
Vaccine coverage for the preschool and teenager booster in London was about 72% during the 2020 - 2021 academic year.
Furthermore, there is clinical evidence that the virus detected in London is genetically linked to the poliovirus detected in Israel and the U.S.
Polioviruses were recently found in New York, both from the case of paralytic polio in an unvaccinated adult in Rockland County and several wastewater samples from local communities.
These findings meet the World Health Organization's criteria for circulating vaccine-derived poliovirus, meaning that poliovirus continues to be locally transmitted.
As of September 2022, the U.S. joined the list of thirty poliovirus-detectable countries.
In the U.S., the IMOVAX Polio® Ipol® IPV polio vaccine has been offered for decades.
This vaccine is generally available as an individual dose and in various combinations. These polio vaccines are available at most clinics and community pharmacies.
And with the Bill & Melinda Gates Foundation's recent $1.2 billion commitment to support efforts to end all forms of polio globally, new innovative polio vaccines may become more accessible.
On October 19, 2022, Kathleen Dooling, MD, MPH, delivered a Poliovirus and Vaccination presentation to the U.S. CDC's Advisory Committee on Immunization Practices meeting.
Additional polio outbreak 2022 news is posted at PrecisionVaccinations.com/Polio.
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