By Caroline Ryan
BBC News Online health staff
Fewer parents are allowing their children to have the controversial MMR vaccine than at any time since it was introduced, official figures have shown.
Parents still have concerns about MMR
In some areas just over half of two-year-olds have been given the measles, mumps and rubella jab - the government says 95% should have been immunised.
BBC News Online looks at why uptake is so poor in these areas, and what is being done to tackle the problem.
Parents across the UK are choosing not to give their children the MMR jab.
It is five years since the first reports suggesting a health risk to children given the vaccine - yet the immunisation rate continues to fall away little by little each year.
This year almost one-in-five children did not get it, and despite smaller scale studies which hint at a modest recovery, health chiefs are desperate for ways to turn the tide for MMR.
Things are particularly bad in London.
In Kensington and Chelsea, just 58% of two-year-olds had been given the MMR vaccination, according to the 2002 to 2003 figures. In Bexley, uptake is scarcely better at 64%.
Low uptake levels are linked to outbreaks of measles, which can be disabling - or even fatal in rare instances.
In February last year, an area of south London was hit by a measles outbreak , which health officials said was due to low MMR uptake.
Many parents remain concerned that the jab could be linked to autism and Crohn's Disease.
Some scientists have suggested there may be a link.
However, no research has ever proved a link, and the overwhelming majority of experts believe the vaccine is safe.
Increasing numbers of parents are turning to single measles, mumps and rubella vaccinations because they distrust official guidance on MMR.
But there is no way of estimating how many have the single vaccine. And public health officials say the gap between vaccinations mean there are periods where children are not immunised - and parents may forget they need to return for addition vaccinations.
Doctors this week warned that parents exaggerate the risk from MMR, while worrying less about realistic risks such as injuries from road accidents.
Researchers from Salford University, writing in the British Medical Journal, say the best way to tackle the problem is to improve communication between doctors and parents.
Now areas with low vaccination rates are taking action to try to allay parents' fears.
In Kensington and Chelsea, health officials have launced a publicity drive to convince parents about the safety of the MMR jab.
Jane Clegg, director of nursing for Kensington and Chelsea Primary Care Trust, told BBC News Online: "We know that we've got a lot of work to do to improve uptake.
"We have people living at both ends of the social spectrum in the area.
"There are people who find it hard to engage with the health services because they have other things in their lives to focus on.
"Then we have people who are very well informed and worried about what they are seeing in the press.
"As a parent, I can understand that, but I hope they will see us as people who can answer their questions."
She said the more affluent families living in the area may also use private GPs, who do not have to submit information about MMR uptake to the trust.
Two years ago, the trust introduced information sessions where health staff hold evening meetings in the community to answer questions about MMR.
Ms Clegg said: "Parents can come along and ask questions. They are given the background and talked through the research.
"There's a lot of debunking of things that they have seen in the press."
She admitted MMR uptake was still low, despite the sessions, but added: "It might have been even lower if we hadn't had them."
Bexley Primary Care Trust has tackled its low MMR vaccination rate by recruiting an immunisation facilitor who is charged with devising ways of addressing the problem.
A spokeswoman for the PCT told BBC News Online: "We're aware that we do have a low uptake.
"But we're not sure it's as low as 64% because there are some issues over date collection from some GP practices."
However, she added: "We have appointed an immunisation facilitor and we are drawing up an action plan.
"We are considering introducing special MMR clinics where there's more time to talk about issues, and perhaps having them on Saturdays. doctors would be able to talk at length about parents' concerns.
"Some clinics may even be held on Saturdays to enable more parents to attend."