Quiet traces of a weakened vaccine virus have surfaced in London's sewage, a reminder that a disease Britain eradicated two decades ago can still slip back across borders and through unvaccinated communities. Health authorities in the capital are now tracing whether the virus has circulated among people in the northeast, and the question they are asking is as much about the protection of children as it is about the virus itself. The finding sits within a long human effort that has cut polio cases by 99 percent since 1988, and it shows how that progress depends on keeping every child's immunisa
Vaccine-Derived Polio Virus Found in London Sewage; No Human Cases Reported
Although we are an island, we are not isolated from the rest of the world.
Mark
Start with the basics. What was actually found?
Mimi
A vaccine-derived type 2 poliovirus in sewage samples from the Beckton treatment works, collected between February and June 2022. No one has been found paralysed.
Mark
So why does it matter if nobody is sick?
Mimi
Because the isolates were genetically related. Usually the UK sees a couple of unrelated detections a year. Related ones point to the virus passing between people.
Luke
Careful, though. "Points to" isn't "proves." The UKHSA says it needs to investigate the extent of transmission. Spread is a concern, not a finding.
Mark
How does a vaccine strain end up in sewage?
Mimi
The oral vaccine uses weakened live virus. A vaccinated person sheds it, and in under-vaccinated communities it can spread and cause paralysis in unprotected people.
Luke
And the import story is the officials' likely explanation, someone vaccinated abroad. It's not confirmed who or how.
Mark
London's coverage is nearly 87 per cent. Is that low?
Mimi
The WHO gave the number, and experts say the concern is pockets of children not up to date, hence the call to check vaccination histories.
Luke
Notably, nobody in the reporting says how many people in northeast London are unprotected. That's still unknown.
Mark
What's the takeaway?
Mimi
Elliman put it plainly: an island is not isolated from the world.
O Pulso
- Vaccine-derived poliovirus type 2 has turned up repeatedly in Beckton sewage samples collected between February and June 2022, and the isolates are genetically linked, which breaks the pattern of scattered, unrelated detections.
- No paralysis cases have been found, but the unsettling possibility of local spread in northeast London has officials moving quickly to trace how far the virus has travelled.
- UKHSA is urging parents and health workers to check vaccination histories, especially for young children, to close gaps where the virus could find people unprotected.
- The likely source appears to be someone recently vaccinated abroad with the oral vaccine, and with London's coverage near 87 percent, the outcome now hinges on whether the checks reach the children who need them.
Quiet traces of a weakened vaccine virus have surfaced in London's sewage, a reminder that a disease Britain eradicated two decades ago can still slip back across borders and through unvaccinated communities. Health authorities in the capital are now tracing whether the virus has circulated among people in the northeast, and the question they are asking is as much about the protection of children as it is about the virus itself. The finding sits within a long human effort that has cut polio cases by 99 percent since 1988, and it shows how that progress depends on keeping every child's immunisation record complete.
On Wednesday, the World Health Organization and British health officials announced that a vaccine-derived strain of poliovirus had been found in London's sewage. No human cases have been identified in Britain, which eradicated the disease two decades ago, but the discovery has set off a careful investigation into how the virus got there and how far it may have spread.
The samples came from the Beckton Sewage Treatment Works, which serves a large part of north and east London, home to around four million people. Britain typically detects a few poliovirus isolates in its sewage each year, but they are usually unrelated to one another. This time, the isolates were genetically related, which suggested that the virus may have moved between people in the northeast of the city.
The virus comes from the oral polio vaccine, which contains weakened live virus that can spread through contaminated water in places where immunisation and hygiene are low. It is weaker than wild poliovirus but can still paralyse those who are unvaccinated. British authorities believe it was likely brought in by someone recently vaccinated abroad, and the WHO has called for the oral vaccine to be phased out in favour of the inactivated version.
Polio expert Kathlene O'Reilly said the best defence is to check vaccination histories, particularly for young children, and to make sure polio protection is up to date. As David Elliman of Great Ormond Street Hospital put it, Britain may be an island, but it is not isolated, and diseases can still arrive from abroad. What comes next depends on the UK Health Security Agency's investigation and on whether those checks reach the children who need them.
On Wednesday, the World Health Organization and British health officials announced that a vaccine-derived strain of poliovirus had turned up in London's sewage. More analysis is underway. No human cases of polio have been found in Britain, where the disease was fully eradicated two decades ago.
The WHO named the strain as type 2 vaccine-derived poliovirus, or VDPV2, found in environmental samples from the British capital. Its statement stressed that the virus had been isolated from those samples only and that no associated cases of paralysis had been detected. It also warned that any form of poliovirus anywhere is a threat to children everywhere.
The UK Health Security Agency said the isolates came from multiple sewage samples collected at the Beckton Sewage Treatment Works in London between February and June 2022. The plant serves a large swathe of north and east London, home to around four million people. A couple of poliovirus isolates are detected in UK sewage in an average year, but they tend to be unrelated to one another. This time the isolates were genetically related, which the agency said prompted the need to investigate how far the virus has been transmitted in northeast London.
The oral polio vaccine contains small amounts of weakened but live virus. It replicates in the gut and can pass to others through faecally contaminated water. The vaccinated child is not harmed, but neighbours can be infected in places where hygiene and immunisation levels are low. The variant is weaker than wild poliovirus but can still cause serious illness and paralysis in people who are not vaccinated. The WHO recorded 959 confirmed cases of VDPV2 worldwide in 2020.
The wider picture is one of enormous progress. Since 1988, when polio was endemic in 125 countries and 350,000 cases were recorded worldwide, cases have fallen by 99 percent. The wild virus now exists only in Afghanistan and Pakistan, yet the vaccine-derived type still causes occasional outbreaks elsewhere. The WHO has called for the oral vaccine to be phased out worldwide in favour of the inactivated polio vaccine. Britain stopped using the oral version in 2004, and British authorities said the virus in the sewage was likely imported by someone recently vaccinated with it abroad.
Polio eradication expert Kathlene O'Reilly said the finding suggests there may be localised spread of poliovirus, most likely among individuals who are not up to date with their immunisations. She said the most effective way to prevent further spread is to check vaccination histories, especially of young children, to make sure polio vaccination is included. The WHO put polio immunisation coverage in London at nearly 87 per cent.
David Elliman, a consultant paediatrician at Great Ormond Street Hospital, said parents sometimes ask why vaccines continue to be given against diseases eliminated in the UK. His answer is that although Britain is an island, it is not isolated from the rest of the world, so diseases can be brought in from abroad. The sewage finding, he said, proves the point.
What to watch next is the UKHSA investigation into the extent of transmission in northeast London, and whether efforts to check children's vaccination histories change the picture.
Citações Notáveis
Any form of poliovirus anywhere is a threat to children everywhere.— World Health Organization
The most effective way to prevent further spread is to check vaccination histories, especially of young children.— Kathlene O'Reilly, polio eradication expert
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