Camden has the lowest percentage of children who have had their first mumps, measles and rubella (MMR) jab by their fifth birthday.
The borough falls well below the 95% target recommended to stop a resurgence of measles.
Only 82.7% of children in Camden received their MMR jab aged five, the lowest figure in England.
Data from the UK Health Security Agency shows that out of 149 local authorities in the country, Camden performed the worst in the five year old category.
Only 69.2 have had their first MMR jab aged two, placing it in 147th position, a huge drop from 80% last year.
Only 62.2% have had both jabs by the age of five placing it at 148.
Barnet and Haringey did not fare much better.
Haringey came second from bottom with 83.1% of five-year-olds receiving their first MMR while for Barnet the figure was 87.5%.
Kirsten Watters, Camden’s director of public health, said: “The number of Camden children who are unprotected against measles, mumps and rubella is extremely concerning.
"These illnesses have not gone away and measles in particular can cause serious illness and death in children. It is also very infectious so even small reductions in coverage increases the risk of outbreaks."
As well as a distinctive rash, measles can lead to severe complications, such as pneumonia and brain inflammation, and sometimes can be fatal.
Vaccination can remove almost all of the risks.
Two doses of the MMR vaccine give 99% protection against measles and rubella and about 88% protection against mumps.
In 2019, the UK lost the elimination status it achieved in 2017.
According to the UKHSA, there has been a significant drop since the start of the Covid pandemic in the number of children getting vaccinated against MMR and other diseases.
As international travel resumes, the UKHSA said it is more likely that measles will be brought in from countries that have higher levels of the disease.
Ms Watters said: "As with the Covid vaccination programme the council is supporting the NHS to increase coverage of childhood immunisations through our new Healthy and Ready for School programme.
"Children should be invited for their first MMR vaccine at age one, and their second at three years and four months.
"If your child has not yet received theirs please urgently contact your GP.“
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