Amelia Down, 14 months, receives the combined measles, mumps and rubella vaccination in Swansea. Photo: AFP
London is holding its breath, trying not to catch the measles.
Experts say a sudden surge in cases of the contagious disease in Wales suggests a vaccination scare 10 years ago is now bearing dangerous fruit.
The densely populated capital, which has some of the most under-vaccinated areas in the country, could be next, as authorities issue urgent pleas for parents to vaccinate their children.
In 1998, Andrew Wakefield published research in The Lancet implying a link between the MMR (measles, mumps, rubella) vaccine and autism.
The research has since been debunked and withdrawn. Wakefield was struck off the medical register and exposed as using dishonest, unethical methods and falsified data.
But his claims, widely spread by the media, terrified a generation of parents. Internet conspiracy theorists kept them alive long after the mainstream considered them discredited, and vaccination rates fell sharply until the mid-2000s. Only in the past year have annual vaccination rates in Britain recovered to their pre-1998 level.
And so, for the first time in two decades, a cohort of children has entered secondary school without enough "herd immunity" to protect the unvaccinated.
"As their social contacts are increasing, so are their chances of catching and developing the disease," epidemiologist Dr Roland Salmon told the London Telegraph.
A government report on measles cases in England in the first three months of 2013 found cases were about the highest recorded since surveillance began in 1994. That follows the 1920 cases confirmed in laboratories last year: then the highest annual figure. Almost one in five cases required hospital treatment.
The age distribution shows a peak in the 10 to 14-year-old age group.
"The predominance of cases being confirmed in secondary school aged children . . . is of particular concern," the report said. "These cohorts have been most affected by the decline in MMR coverage in the early part of the century."
Parents have been queuing to vaccinate their children at clinics in the south Wales city of Swansea, where a measles outbreak has so far infected almost 1000 people.
Professor David Salisbury, director of immunisation at the Department of Health, told the Sunday Times any outbreak in London "could have the same effect multiplied by the difference in size". There are almost 10 million people in London, 40 times the population of Swansea.
Dr Mary Ramsay, head of immunisation at Public Health England, said: "We have potential for school outbreaks in many areas of the country.
"The areas most likely to be affected would be London and the south and east of the country, where we know that the historical [MMR] coverage was not as high."
The government estimates about 330,000 children aged 10 to 16 in England and Wales are unvaccinated and another 330,000 did not get a second booster shot.
Many of the country's areas with the lowest MMR uptake are around London. In Brent, in the north-west of the capital, only 46 per cent of children aged 10 are on record as having had both vaccine doses. Other at-risk areas include the posh suburbs of Kensington and Chelsea, trendy Camden and middle-class centres on the city's northern edge.
London Mayor Boris Johnson told the media they should apologise for their role in the "great MMR panic", as he convened his public health team for an urgent briefing on the risk of a major outbreak.
Investigative journalist Brian Deer, who originally exposed Wakefield, wrote on the weekend that the South Wales Evening Post had "frightened its readers like no other tabloid" with emotive headlines such as "Stop giving our children jabs".
"No wonder parents' fears spread like an infection around Swansea," Deer wrote. "And no wonder a real infection would one day take hold."
But Deer said he was concerned the pendulum might now have swung too far the other way. "To me the . . . real issue is the integrity of the scientific process," he said. "How could it be that [Wakefield's] research . . . could have gone unchallenged for so long?
"Medicine has no regulation at all, but there's this idea now that everything is fine with vaccines and medicine.
"You have to wonder whether [we] are at risk of letting our guard down for fear of doing the same thing again."