Almost a million children aged one to nine across London will be offered the polio vaccine to try to prevent the spread of the virus.
Health officials have warned that there has been “some transmission” of the virus in the capital after detecting poliovirus in sewage samples.
Although officially eradicated in the UK in 2003, polio can cause paralysis in rare cases and can be life-threatening.
While there have been no confirmed cases, officials sounded the alarm over the rising number of samples found in sewage in London.
Children aged five in England who had not received DTaP/IPV pre-school booster in 2020/21 (PA)
The UK Health Security Agency (UKHSA), working with the Medicines and Healthcare products Regulatory Agency (MHRA), found poliovirus in sewage samples in London boroughs including Barnet, Brent, Camden, Enfield, Hackney, Haringey, Islington and Waltham Forest.
It was first detected at Beckton sewage treatment works earlier this year.
Officials said levels of the virus found in sewage and their “genetic diversity” suggests “some virus transmission in these boroughs”.
As a result officials are to launch a rapid vaccination programme among youngsters in London, where there are lower levels of uptake of the vaccine.
Vaccination rates in the capital are well below recommended levels and there is a risk that “under-vaccinated” children can pass the infection to others.
Youngsters can be responsible for “silent transmission” of polio, which means that they may have the virus but not show any symptoms.
Children in London aged one to nine who are not yet fully vaccinated will be offered a catch-up dose, while those who have already been fully vaccinated will be offered a booster.
Youngsters will be offered a jab within the next four weeks with officials hoping to vaccinate all those invited within six weeks.
The NHS in London will contact parents when it their child’s turn to get the vaccine, with parents urged to take up the offer “as soon as possible”.
The programme will start in the areas where the virus has been detected in sewage and then be extended across all London boroughs.
The virus has not yet been found outside London but officials are stepping up surveillance across the rest of the country.
Nationally the overall risk of paralytic polio is considered “low” by the UKHSA.