Polio is thought to be circulating in a patch of north London, which also the lowest proportion of vaccinated children in England.

Camden, Enfield, Hackney, Haringey and Islington occupied the bottom five places on the latest table showing English local authorities' polio booster jab uptake.

In all five boroughs, the latest quarterly analysis showed over a third of young children who should have received boosters had not had them.

The jabs should be given between the ages of three years four months, and five years.

The UK Health Security Agency (UKHSA) asked GPs what proportion of children who turned five between January and March had received them.

In all five neighbouring boroughs, many had not.

The low vaccination rate coincided with polio samples being found in all five boroughs' sewage.

Those results, said Camden Council, "suggest that community transmission is taking place".

What is the risk?

It is thought that the virus arrived in visitors from countries which still use an oral vaccine, where a weakened version of the live virus is swallowed.

No clinical cases have yet been detected, said Haringey Council, and the risk “is low at this stage”.

But, it added, there is a risk that polio could spread, “particularly in communities where vaccine uptake is lower".

In some cases, this could cause paralysis or death.

“The risk of illness among unvaccinated children is real, not just for polio but also for other vaccine-preventable diseases such as measles,” warned Dr Sandra Husbands, Hackney’s director of public health.

The figures

The World Health Organisation (WHO) says 95 per cent full vaccination is needed to achieve herd immunity.

As of March 2022, Hackney had the lowest polio booster uptake in England: 55pc.

Camden’s was 60pc, Haringey’s 64pc and Islington and Enfield’s 66pc.

Four of the boroughs – Hackney, Camden, Haringey and Islington – were also in the bottom five in the previous quarter.

As of March 2022, Hackney and Haringey were also at the bottom of the table for primary vaccines, given to babies.

Hackney, Haringey and Camden had been in the bottom five on that measure the previous quarter as well.

The UKHSA noted that the latest data was incomplete.

In Hackney, three GP practices’ data was missing. In Camden it was two and in Haringey it was one. Hackney’s data also included the City of London.

Why so low?

Public bodies have suggested several reasons for low uptake.

One, said Haringey, is a general NHS backlog due to Covid-19 – but that is true in all boroughs.

Two councils suggested north London's demographics were a factor.

Islington said the affected boroughs had “a lot of mobility”, and families moving around made it harder for GPs to keep track.

It also mentioned diversity and poverty, as did Hackney.

“Hackney is one of the most diverse boroughs in London, as well as one of the boroughs with significant deprivation,” said Dr Husbands.

“There is significant variation in the uptake of immunisations across the borough and between different populations and groups."

This was a long-standing problem, she said, with “particularly low uptake in certain communities and groups”.

She said this was also true of the neighbouring boroughs.

“These boroughs share the characteristics of high levels of diversity and pockets of deprivation,” she said.

What now?

Since polio was found in sewage, boroughs are working with the NHS to promote a vaccination drive.

NHS North East London said it had 224 “community champions", trained to promote the jabs to "diverse communities".

Rabbi Herschel Gluck, president of Hackney’s Shomrim, is working with the NHS to promote the vaccine to the Orthodox Jewish community.

He said vaccine hesitancy is “not an issue”, as the faith “puts tremendous importance on protecting life”.

“I don’t think the problem is in the community,” he said. “I think it’s largely within the NHS and the authorities, that they haven’t really tried to understand how to best communicate with the community.

“Hopefully we will achieve that all will become aware of the need to vaccinate.”

NHS North East London said: “Our recent vaccination clinics for the Jewish community in Stamford Hill have been well-attended.

“We encourage everyone to take up their vaccine offer when contacted, or visit our website for more information.”

For more information, visit www.nhs.uk/conditions/polio/