The government has launched a campaign to raise MMR vaccination rates in England amid growing concerns about a measles epidemic.
The Department of Health has asked primary care trusts (PCTs) to offer the jab to all children up to the age of 18 not already fully protected.
Extra vaccine supplies and funding are being made available.
An epidemic of measles, which can be fatal, could potentially affect up to 100,000 young people in England alone.
The MMR vaccine protects against measles, mumps and rubella. Experts say it is perfectly safe, but vaccination rates dipped following controversy about its safety. A study which raised the possibility that MMR was linked to autism has since been dismissed by the vast majority of research, but levels of public confidence in the jab have still not fully recovered.
In a letter to all PCTs, the Chief Medical Officer Sir Liam Donaldson asks health bosses to urge parents to get their children immunised.
The number of cases of measles in England is rising following a decade of relatively low vaccine uptake.
In 2006 and 2007 there were 1,726 confirmed cases in England and Wales – more than the previous 10 years put together.
From 1996 to 2005 there was a total of 1,621 confirmed cases.
Scientific advice from both the Department of Health and the Health Protection Agency suggests vaccination levels need to be increased as a matter of urgency.
© Immediate Media Company Ltd 2012. This website is owned and published by Immediate Media Company Limited. www.immediatemedia.co.uk