Health officials in Britain warned parents to ensure their children have been vaccinated against polio after the virus that causes the disease was found in London sewage samples in recent months. The UK Health Security Agency said it believes the virus was “vaccine-derived”, meaning it came from someone who received the live polio vaccine abroad. That person would then have passed the virus to closely linked individuals in London, who shed the virus into their faeces. The UK stopped using the live oral polio vaccine in 2004 and switched to an inactivated version. Polio, which was officially eradicated in the UK in 2003, can cause paralysis in rare cases and can be life-threatening. Health Secretary Sajid Javid said he was “not particularly worried” about the news, while health authorities stressed that the risk to the public overall is “extremely low”. They added that the virus has been detected only in sewage samples, and no cases of paralysis have been reported. Still, health authorities have established a “national incident” to check for cases elsewhere as a precaution. Massive ‘fatberg’ discovered at English seaside resort in Devon They also asked people to check that their children are fully vaccinated and to contact their doctor if unsure. “Most of the UK population will be protected from vaccination in childhood, but in some communities with low vaccine coverage, individuals may remain at risk,” said Dr Vanessa Saliba, an epidemiologist at the health agency. “Vaccine-derived polio virus has the potential to spread, particularly in communities where vaccine uptake is lower,” she said. About 94 per cent of two year-olds in the UK have been vaccinated against polioviruses, according to data from the National Health Service. London faces a wider challenge, however, as its infant vaccination rate is lagging behind the national level, with 89 per cent of two year-olds immunised. While this kind of event is effectively unheard of in Britain, vaccine-derived polio virus is a known, albeit rare, threat globally in countries with low immunisation coverage. It can cause outbreaks, and Ukraine and Israel recently reported cases. Outbreaks are more common in countries including Nigeria and Yemen. The last polio case in the UK was in 1984, and “wild” polio is now only found in Afghanistan and Pakistan, with imported outbreaks reported in Malawi and Mozambique in 2022. The United States has been polio-free since 1979. The World Health Organization’s Director General, Tedros Adhanom Ghebreyesus, said that the agency was working with the UK on the response. “Surveillance, vaccination and investment to end polio is critical,” he tweeted. Associated Press, Reuters and Bloomberg