Young children in east London will be offered a polio booster vaccine after further cases of poliovirus were found.

Positive samples of vaccine-derived poliovirus have been detected in sewage across a number of north London boroughs, following the discovery in samples at the Beckton sewage treatment works earlier this year.

The Joint Committee on Vaccination and Immunisation (JCVI) has advised that a targeted inactivated polio vaccine booster dose should be offered to all children between one and nine in every London borough.

The UK Health Security Agency (UKHSA) stressed that there have been no confirmed cases of polio and that the risk to the wider population is low.

The virus can cause paralysis in a small number of cases but the UKHSA said most people with polio fight it off without realising they are infected.

Dr Vanessa Saliba, consultant epidemiologist at UKHSA, said: "The last case of polio in the UK was in 1984, but decades ago before we introduced the polio vaccination programme around 8,000 people would develop paralysis every year.

"It is vital parents ensure their children are fully vaccinated for their age.

"Following JCVI advice all children aged one to nine years in London need to have a dose of polio vaccine now – whether it’s an extra booster dose or just to catch up with their routine vaccinations.

"It will ensure a high level of protection from paralysis. This may also help stop the virus spreading further."

The NHS will contact parents when it is their child’s turn to come forward for a booster or catch-up polio dose.

The move comes after at least one positive sample of the poliovirus is present in parts of Barnet, Brent, Camden, Enfield, Hackney, Haringey, Islington and Waltham Forest.

The UKHSA said sampling has also detected the virus in lower concentrations and frequency in areas next to the south and east of Beckton.

A spokesperson said: "It is not clear whether the virus has established itself in these areas or if the detections are due to people from the affected area visiting these neighbouring areas."

The polio booster programme will start with the areas where the poliovirus has been detected and vaccination rates are low.

This will be followed by rapid rollout across all boroughs, the spokesperson added.

Further sewage sampling is also taking place at other London sites to assess the extent of the virus spread.