The UK’s Health Security Agency (UKHSA), working with the Medicines and Healthcare products Regulatory Agency (MHRA), detected poliovirus in wastewater samples collected from the London Becton sewage treatment plant.
As part of routine surveillance, it is normal for 1 to 3 ‘vaccine-like’ polioviruses to be detected each year in sewage samples in the UK, but these have always been one-off findings that have not been re-detected. These previous findings occurred when an individual vaccinated abroad with live oral polio vaccine (OPV) returned or traveled to the UK and briefly ‘shed’ traces of the vaccine-like polio in their faeces.
Investigations are underway after several closely related viruses were found in sewage samples taken between February and May. The virus continues to evolve and is now classified as “vaccine” poliomyelitis type 2 (VDPV2), which can rarely cause serious illness, such as paralysis, in people who are not fully vaccinated.
The discovery of a VDPV2 suggests that there may have been some spread between closely related individuals in North and East London and that they are now shedding the type 2 poliovirus strain in their faeces. The virus has only been found in sewage samples and no associated cases of paralysis have been reported – but investigations will aim to establish whether community transmission is taking place.
The last case of wild polio contracted in the United Kingdom was confirmed in 1984. The United Kingdom was declared polio-free in 2003.
Dr. Vanessa Saliba, consultant epidemiologist in UKHSA said:
Vaccine-derived poliovirus is rare and the risk to the general public is extremely low.
Vaccine-derived poliovirus has the potential to spread, particularly in communities where vaccine uptake is lower. In rare cases it can cause paralysis in people who are not fully vaccinated, so if you or your child are not up to date with your polio vaccinations, it is important to contact your GP to catch up or if you have not sure, check your Red Book. The majority of the UK population will be protected by childhood vaccination, but in some communities with low vaccine coverage people may remain at risk.
We are urgently investigating to better understand the extent of this transmission and the NHS has been asked to report any suspected cases of UKHSAalthough no cases have been reported or confirmed to date.
Jane Clegg, NHS Chief Nurse in London, said:
Most Londoners are fully protected against polio and will not need to take any further action, but the NHS will start contacting parents of children under 5 in London who are not up to date with their polio vaccinations to invite them to be protected.
In the meantime, parents can also check their child’s vaccination status in their Red Book and people should contact their GP to book a vaccination if they or their child is not fully up to date.
The UK is considered by the World Health Organization to be a polio-free country, with a low risk of polio transmission due to the high level of vaccination of the population. However, vaccination coverage for childhood vaccines has fallen nationally and particularly in parts of London over the past few years, so UKHSA urges people to check they are up to date with their vaccinations.
Effluent monitoring is being expanded to assess transmission rates and identify local areas for targeted action. Health professionals have been alerted to these findings so they can immediately investigate and report anyone who has symptoms that could be polio, such as paralysis.