Concern about polio in London became official in June when the UK Health Security Agency (UKHSA) reported that “several closely-related viruses were found in sewage samples taken between February and May” at the Beckton sewage treatment works. It looked likely to the UKHSA at the time that “there has been some spread between closely-linked individuals in North and East London”.
Today, in a bid to reduce further spread, it’s been announced that all children in Greater London aged between one and nine-years-old will be offered a polio vaccine – about 900,000 children altogether, including those who are already fully vaccinated.
Polio viruses have since been detected in eight boroughs: Barnet, Brent, Camden, Enfield, Hackney, Haringey, Islington and Waltham Forest. A total of 116 examples have been identified in 19 sewage samples as of 5 July.
Polio, which can cause paralysis, was officially deemed eradicated in Europe in 2003 and the NHS says there have been “no confirmed cases of paralysis due to polio caught in the UK since 1984”. Why, then, has it returned, what brought it to London, and what dangers does it present?
The UKHSA explained in June that it is normal for up to three polioviruses to be detected in UK sewage samples each year and then to disappear. They are caused by individuals vaccinated against the virus overseas “shedding” traces of the live virus used in the vaccine, administered orally, in their faeces. This type of vaccine is not used in the UK.
The UKHSA statement today says that most of what they’ve found has been “vaccine-like virus” but a few have mutated sufficiently to be classified as vaccine derived poliovirus 2 (VDPV2), which “behaves more like naturally occurred ‘wild’ polio and may, on rare occasions, lead to cases of paralysis in unvaccinated individuals”.
Polio has been around since ancient times, but the first definitive description of it was not published until 1789, by the pioneering London-based physician Michael Underwood. Polio epidemics, such as in Oslo in 1868 and Brooklyn in New York in 1916, did not occur in western cities until the late 19th century, ironically because natural immunity declined as hygiene improved.
Jane Clegg, the chief nurse for the NHS in London, said most Londoners are protected from polio, but vaccine doses are being urgently offered to the parents of one-to-nine-year-olds who aren’t up to date with their jabs, and as boosters for those whose children in that age group are. Increased sampling of London’s sewage will begin in the coming days and sites will be set up outside the capital to determine if the virus is spreading beyond it.
Photograph from Beckton Sewage Treatment Works.
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