New measles outbreak fears
Britain is reaching a "danger zone" threatening larger outbreaks of measles because of a dip in childhood vaccination.
The number of measles cases in England and Wales has increased while confidence in the combined MMR vaccine has fallen.
A research team has found the average number of new infections that an infected person causes is increasing.
The team Royal Holloway, Imperial College London and the Health Protection Agency studied data from recent outbreaks to show a trend towards larger clusters of cases in the UK.
The researchers said that as the rates of early childhood vaccination dipped, the so-called reproductive number was rising to approach the point where UK outbreaks may not just fizzle out.
The report found that the reproductive number rose from 0.47 between 1995 and 1998, to 0.82 in 1999-2002.
Cases and small outbreaks in the UK tend to occur where people bring measles into the country from abroad.
The report noted that if the reproductive number increased to exceed one, the infection would not disappear as it does at the moment after every case or small outbreak.
Paper author Vincent Jansen, a Wellcome Trust researcher from Royal Holloway in London, said: "My hope is that this is a warning for the parents.
"We are approaching the danger zone where measles could once again become an endemic disease in the United Kingdom."