PremiumThe UK health authorities said that the risk of infection from the disease, which causes paralysis in children in under 1% of cases, is low currently because of high vaccination rates
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The public health officials have declared a national incident and issued a nationwide appeal for parents to ensure their children's vaccines are up to date after several samples of vaccine-derived poliovirus were found during routine London sewage testing.
According to the UK Health Security Agency (UKHSA), several closely related viruses were found in samples taken in north and east London between February and May. The findings suggest some spread between closely linked individuals.
The virus has continued to evolve and is now classified as a “vaccine-derived" poliovirus type 2 (VDPV2), which on rare occasions can cause serious illness, such as paralysis, in people who are not fully vaccinated.
The health agency is working with other bodies, including the World Health Organization, to urgently investigate the matter to understand the extent of the transmission.
"It is important to note that the virus has been isolated from environmental samples only," the WHO said, stressing that "no associated cases of paralysis have been detected."
But it warned, "any form of poliovirus anywhere is a threat to children everywhere."
The discovery is cause for concern as the UK’s last case of wild polio was in 1984 and the country was declared polio-free in 2003.
Risk is low
The health authorities have, however, said that the risk of infection from the disease, which causes paralysis in children in under 1% of cases, is low currently because of high vaccination rates.
“Vaccine-derived poliovirus is rare and the risk to the public overall is extremely low," said Dr Vanessa Saliba, consultant epidemiologist at UKHSA.
“Vaccine-derived poliovirus has the potential to spread, particularly in communities where vaccine uptake is lower. On rare occasions 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’s important you contact your GP," she said.
Nationwide vaccination levels are above the 90% needed to prevent outbreaks, but London's coverage rates among the under-twos have dipped below that in recent years.
“The majority of Londoners are fully protected against Polio and won’t need to take any further action, but the NHS will begin reaching out to parents of children aged under five in London who are not up to date with their Polio vaccinations to invite them to get protected," said Jane Clegg, chief nurse for the NHS in London.
The primary polio vaccine course is given to babies at two, three and four months. Three doses are needed to complete the primary course. In the UK it is given as part of the six-in-one vaccine.
How did the detection occur?
In the past, UKHSA said the detections occurred when an individual vaccinated overseas with the live oral polio vaccine returned or travelled to the country, and briefly shed the virus in their faeces.
They believe this is also what happened this time, with the key difference being that the virus has also probably spread between closely linked people.
Investigations into community transmission were ongoing, the agency said.
Wastewater surveillance is being expanded to assess the extent of transmission and identify local areas for targeted action.
UKHSA said that healthcare professionals have been alerted to these findings so they can promptly investigate and report anyone presenting with symptoms that could be polio, such as paralysis.
