A measles awareness roadshow is being held in Leeds in an attempt to get more parents to give their children the measles, mumps and rubella jab.
The city has been named one of the worst parts of the country for the uptake of the MMR vaccine.
Parents will have the chance to talk to health professionals at the event at Briggate.
Other areas at risk are being targeted, with the roadshow visiting All Saints Square in Rotherham on 12 August.
The Department of Health said recent estimates suggested more than two million children in England are at risk from the disease because they have missed either their first or second MMR vaccination.
Professor David Salisbury, director of immunisation at the Department of Health, said: "The number of cases of measles is on the increase and we need to warn all parents about the potential dangers of this infection.
"They need to be aware that if their child is not immunised and comes into contact with a child infected with measles, there is around a 90% chance they will catch measles."
Leeds was named as one of the worst parts of the country for uptake of the measles, mumps and rubella vaccine
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