The detection of polio in UK sewage samples has prompted advice for people to ensure their vaccines for the virus are up to date.
Polio, which was officially eradicated in the UK in 2003, can cause paralysis in rare cases and can be life-threatening.
Most people who get polio do not have symptoms but some suffer mild, flu-like issues such as a high temperature, extreme tiredness, headaches, vomiting, a stiff neck and muscle pain.
The UK Health Security Agency (UKHSA), working with the Medicines and Healthcare products Regulatory Agency (MHRA), has found polio in sewage samples collected from the London Beckton Sewage Treatment Works, which serves around four million people in north and east London.
The finding has prompted health officials to urge people to check their vaccines – and those of their children – are up to date.
How do I check my vaccine?
The polio vaccine is given on the NHS when a child is eight, 12 and 16 weeks old as part of the 6-in-1 vaccine. It is given again at three years and four months old as part of the 4-in-1 (DTaP/IPV) pre-school booster, and at 14 as part of the 3-in-1 (Td/IPV) teenage booster.
All of these vaccines need to have been given for a person to be fully vaccinated, though babies who have had two or three doses will have substantial protection.
Watch: Polio virus detected in UK
People must have the full course of polio vaccines to be fully vaccinated against the virus.
To check whether your child is due a vaccine, you must request their health records from the GP practice they are registered with.
Any person with parental responsibility can request the records of a child who is aged 12 or younger.
Children aged 13 or over can get their immunisation history digitally by logging into their online account using the NHS app or website once registered for online services.
If your child is not registered with a GP, the records will be held by Primary Care Support England (PCSE) on behalf of NHS England.
How many children haven't had the vaccine?
Official figures analysed by the PA news agency show that of the 693,928 children in England aged five in 2020/21, some 592,191 (85.3%) had received their polio booster by their fifth birthday while 101,737 (14.7%) had not.
Around a third of all these unprotected five-year-olds were in London (34,105). The figures for England are:
South-west England - 10.3%
Eastern England - 10.4%
Yorkshire and the Humber - 10.8%
South-east England - 11.4%
North-west England - 13.8%
West Midlands - 15.1%
Separate UKHSA data shows that of the 625,379 Year 10 children in England in the academic year 2020/21, 502,247 had received the teenage booster (80.3%), while 123,132 (19.7%) had not.
How worried should we be?
While it is normal for polio to be picked up as isolated cases and not detected again, experts have raised the alarm after several genetically-linked viruses were found in samples between February and May.
This evolved form of the virus, classified as a ‘vaccine-derived’ poliovirus type 2 (VDPV2), has changed over time and behaves more like the “wild” or naturally-occurring virus – meaning it can be spread more easily to people who are unvaccinated and who come into contact with the faeces or coughs and sneezes of an infected person.
The UKHSA stressed that the virus has only been detected in sewage samples and no cases of paralysis have been reported.
Dr Vanessa Saliba, consultant epidemiologist at UKHSA, said: “Vaccine-derived poliovirus is rare and the risk to the public overall is extremely low.”
However, she warned that it can cause paralysis in people who are not fully vaccinated “on rare occasions”.
Health secretary Sajid Javid said he was “not particularly worried” about the detection of polio when asked this morning.
He told BBC Radio 4’s PM programme that UKHSA “reminded me that as a country we have very high vaccination rates against polio. We’ve been declared polio free since 2003 and we haven’t had any cases since then”.
He added: “But as a precaution, sensibly what the NHS will be doing in London is contacting those families that have children age five or below and just making sure they’re up to date with their polio vaccination status.”
Sir Jeremy Farrar, a former professor of tropical medicine at the University of Oxford, said this morning that we should take the detection of the virus “seriously” but added to the BBC Radio 4’s Today programme: “Do the surveillance and make sure surveillance is there all the time.. and we’ll be able to cope with these polio viruses and we won't have polio cases in the UK.”
Urgent medical attention should be sought if people experience rapid onset of weakness in a limb, which will be floppy, or difficulties with breathing.