London could see a measles outbreak of tens of thousands of cases unless vaccination rates improve, the UK Health Security Agency has warned.

In response, NHS England has launched a national campaign encouraging people to check their vaccination status, particularly targeted towards people living in the capital.

So far this year, there has been 128 cases of measles across all regions of the UK – more than double the total amount for the whole of last year, when 54 cases were reported.

More than half (65%) of the cases were in children under the age of 10 years, and 20% were in teenagers and young people aged 15 to 34 years.

UKHSA said that less than one in five (24 out of 128, or 19%) of the cases were imported or import-related, while the rest reflect community transmission in England.

And 66% of this year’s total number of cases have been found in London.

The UKHSA warned that a measles outbreak of between 40,000 and 160,000 cases could occur in the capital due to lower levels of vaccination coverage.

In some groups and areas of London, just 69.5% of two-year-olds have had the first measles, mumps and rubella (MMR) dose, which is part of the NHS Routine Childhood Immunisation Programme.

This means that by the time they start school, around 20% of children in London will be unprotected against measles, compared to 10% in England as a whole.

The UKHSA said that low vaccination rates over several years had been exacerbated by the Covid-19 pandemic.

In particular, the UKHSA said there was a high risk of cases linked to overseas travel, leading to outbreaks in specific population groups such as young people and under-vaccinated communities.

It said that 19- to 25-year-olds were particularly susceptible as some may have not received vaccination as a child due to concerns around the vaccine in the early 2000s based on a study by Andrew Wakefield which was found to be unfounded, and some may still not be fully vaccinated as adults.

And it urged anyone of any age who had not received the MMR vaccination, or parents of children who were unvaccinated, to come forward.

This is particularly important if travelling overseas this summer, the UKHSA said, adding that achieving high vaccination coverage across the population would help to protect infants under one who had not yet had the vaccination, as well as other vulnerable groups.

The World Health Organization recommends that 95% of the population are vaccinated against measles to prevent outbreaks.

Jane Clegg, regional chief nurse for the NHS in London urged those with questions or concerns to contact their GP or local pharmacist for advice.

‘Now’s the time to act to protect yourself and loved ones from measles,’ she added.

Meanwhile, Dr Vanessa Saliba, UKHSA consultant epidemiologist said: ‘Measles can be a serious infection that can lead to complications especially in young children and those with weakened immune systems.

‘Due to longstanding sub-optimal vaccine uptake there is now a very real risk of seeing big outbreaks in London.’

She reiterated the importance of being fully vaccinated, especially before travelling overseas this summer, and added: ‘Nobody wants to see their child or loved ones sick with measles, or put others who are more vulnerable, like babies, at risk. I urge those who have missed their MMR vaccines to catch-up now.’