Q&A: Measles and MMR
Measles can be a very serious disease - and children who have not been vaccinated are at risk.
What is measles?
Measles is a highly contagious infectious disease characterised by a high fever, a rash and generally feeling unwell.
The first symptoms include runny nose, sore eyes, a cough and fever.
Around the fourth day of the illness, a rash - flat red or brown blotches - may appear, usually starting on the forehead and spreading downwards.
There may also be diarrhoea, vomiting and abdominal pain.
While this may be the full extent of the illness in many, resolving itself within two weeks of the first symptoms, other complications may arise in about one in 15 cases.
These include a severe cough and breathing difficulties, ear infections, pneumonia and eye infections.
In a very small number of cases, inflammation of the brain (encephalitis) may follow. This is extremely dangerous, as 25% of those affected are left with brain damage.
The most severe complication of measles - occurring in only one in 100,000 cases - is a slowly-progressive brain disorder which does not normally show until some time after the original infection, causing seizures and even death.
Globally, measles is still one of the biggest childhood killers. The World Health Organization estimates there are 430 deaths from measles every day. It is thought that between one in 1,000 and one in 3,000 of those infected will die.
What is MMR?
MMR is a combined vaccine against measles, mumps and rubella, three common infectious diseases of childhood.
It was introduced in the UK in 1988 to replace single vaccines for each disease.
It is used in countries throughout the world, with millions of doses delivered each year.
The first MMR vaccine is given on the NHS as a single injection to babies as part of their routine vaccination schedule, usually within a month of their first birthday.
They will then have a second injection of the vaccine, known as the MMR booster, before starting school, usually between the ages of three and five.
The first gives about 95% protection against measles, while two doses gives 99-100% protection.
Why were people worried about it?
In 1998, a study published in the respected journal The Lancet raised the possibility that the jab may be linked to autism and bowel disease.
The paper and the media furore that followed prompted many parents to decide against having their children vaccinated with the three-in-one jab.
Some opted to have their children vaccinated using single vaccines for each disease. However, others decided against having their children vaccinated against these diseases at all.
Mumps, measles and rubella are all serious diseases, particularly measles. Many doctors were concerned that a drop in vaccination levels could leave many children at risk.
What has been the long-term effect?
To ensure that all children in a community are protected from measles, 95% of them need to be fully vaccinated - this is known as herd immunity.
In the wake of the publicity surrounding the Lancet paper vaccination rates fell sharply.
At its lowest, in 2003/4, fewer than eight in ten children were vaccinated - but in some areas less than half of children received the jab.
Health experts believe there are more than one million schoolchildren in England alone who are not protected against the disease.
The gloomy predictions of experts have been borne out, with cases of measles increasing.
There were 2,016 confirmed cases of measles in England and Wales in 2012, the highest total for 18 years.
The current outbreak in Wales, in which more than 800 cases have been recorded, is the biggest single outbreak in the UK since the controversy.
Was there any reason to be worried?
No. No authoritative research has been published to back up claims that it may be linked to autism and bowel disease.
The Wakefield claims have been tested in over a dozen statistical studies carried out across large populations in different countries, and none found any evidence at all to suggest there was any link between the MMR jab and autism.
These studies included a 2004 investigation by a team from the UK Medical Research Council which compared the vaccination records of 1,294 children diagnosed with autism or related conditions with those of 4,469 children who had no such diagnosis.
Overall, 78% of the children with autism had received MMR. But 82% of the other children had also been given MMR.
A 2005 paper looked at autism rates among 31,426 children born in Japan. It found the incidence of autism actually increased after the MMR jab was withdrawn in the country in 1993.
One of the biggest studies of all - a 2002 paper examining the records of 537,303 children born in Denmark - also showed no link between MMR and autism.
What about the original study?
The Lancet, which published the controversial MMR paper in the first place, has since publicly announced it should never have printed it.
Dr Andrew Wakefield, the man behind the work, was subsequently struck off the medical register by the General Medical Council for serious professional misconduct.
A GMC panel found that Dr Wakefield had acted "dishonestly and irresponsibly" while carrying out his research.
Among the charges of which he was found guilty was paying children £5 for blood samples at his son's birthday party.
What about adults?
The MMR vaccine was introduced in 1988. Prior to that a licensed vaccine to prevent measles first became available in 1963, an improved measles vaccine in 1968.
Most adults born before 1970 in the UK are likely have had measles infection and therefore be immune.