The controversial combined vaccine for measles, mumps and rubella has been linked to a rare bleeding disorder in children.

However, health experts say the finding should not dissuade parents from getting their children vaccinated with the MMR vaccine.

The Department of Health has insisted MMR is safe, despite concern that it may be linked to autism and bowel disorders in children.

Now a new study has found a link between the vaccine and a disorder called idiopathic thrombocytopenic purpura (ITP) which leads to bleeding under the skin.

Victims feel tired and feverish and develop a purple rash on their skin which can turn black and spread over the body.

In extreme cases, the spleen may have to be removed or a blood transfusion given.

However, most people suffer from an uncomfortable but mild form and can be easily treated with drugs.

The disorder is caused by a shortage of platelets, the cells that give blood its "stickiness".

About one in 10,000 people has the condition. In children, it is often preceded by a viral infection.

Records

The researchers, from the Public Health Laboratory Service (PHLS) and the Royal Free Hospital, London, analysed records on hospital admissions for ITP.

The records included all children under the age of five admitted within six weeks of MMR vaccination in the South East Thames and North East Thames regions between October 1991 and September 1994.

There were 28 admissions for 21 children up to the age of two who had been vaccinated with MMR.

Of these, nine children had been admitted within six weeks - none had had ITP before.

Combining data from a previously published study, the authors calculated that two out of every three cases of ITP in the six weeks after immunisation are caused by MMR.

One in every 22,300 MMR vaccinations will result in admission to hospital for ITP, they say.

There is as yet no data on booster doses and the risk of ITP.

The children whose illness was associated with MMR tended to have milder symptoms and spent less time in hospital than those whose ITP was not associated with the vaccine.

Children who had already had ITP were at no greater risk of recurrence as a result of the vaccination, the study indicated.

Small risk

Dr Elizabeth Miller, head of the Immunisation Division at the PHLS Communicable Disease Surveillance Centre, said: "Although our study shows that some children are admitted to hospital for ITP, even in these cases the disease is rarely dangerous and can be easily treated.

"This is in stark contrast to measles, mumps and rubella which can have very serious consequences and be difficult to treat.

"The risks associated with ITP are small when compared to those of the diseases which this vaccine is designed to prevent.

"We urge parents to protect their children against measles, mumps and rubella with the MMR vaccine."

Recent figures showed that despite ongoing concerns about the safety of the MMR vaccine, immunisation rates had stopped falling. However, rates in some areas are as low as 75%, not high enough to prevent an outbreak of measles.

Campaigners want single dose vaccines for measles, mumps and rubella to be made available to parents who want them.

However, the Department of Health says that single dose vaccines are not effective.

The research is published in the journal Archives of Disease in Childhood.