The MMR vaccine is the subject of much controversy
It should be a straightforward decision. After all the scientific evidence is overwhelming - the Department of Health, the World Health Organisation and American bodies have all declared that MMR is safe.
But still some parents hesitate, worried by scare stories in the media about an unproven link between the triple jab and conditions such as bowel disease or autism.
BBC health correspondent Chris Hogg reports on the battle officials face as they try to win over those doubters whose refusal to have their children vaccinated could be jeopardizing public health.
The debate over the controversial MMR vaccine could prove to be the most important single public health issue of Labour's time in office.
There is real worry from public health officials in some areas that falling vaccination levels will lead to a resurgence of disease.
In the 1970's a scare about the whooping cough jab caused vaccination levels to tumble to 30%.
Isolated research may have suggested that the combined measles, mumps and rubella vaccine is linked to an increased risk of autism and bowel disorders.
But the overwhelming body of medical opinion is that the vaccine is absolutely safe.
However, for people like Rachel Oliver, a health visitor from Oxfordshire, persuading sceptical parents is no easy matter.
As one mother puts it: "Can it just be media hype? Why are Tony Blair and people like that not saying that they've had it?"
The government has bombarded health professionals with information about the vaccine.
But Rachel Oliver acknowledges that for many parents the science isn't enough - in the end they will make a choice based purely on emotion.
"We are hugely aware of the incredibly difficult decision parents have to make and that the messages that they have to balance out are almost too much for anybody."
Daytime television
This confusion makes MMR good fodder for the daytime TV talk shows.
Government research shows that parents trust TV doctors more than almost anyone else on this issue.
Dr David Bull, from Watchdog Healthcheck, admits that he and his colleagues can be put in a difficult position by the producers of the shows they work on.
Scare stories make for better television. There's often pressure to cover the latest twist or turn whether the research stands up to scrutiny or not.
As Dr Bull says: "There's always a tension. I think as a journalist you're always looking for a good story.
"Probably more than any of the team I'm worried about the medical information that we're giving out."
Balanced coverage
Most journalists would argue that their coverage of the MMR issue has been balanced.
"There is no doubt that media reporting does have a clear effect.
"If you're writing a story clearly you want to make it interesting but never the less there is a responsibility on the journalist to achieve balance.
"If you show two sides of a story and give them both equal weighting that's fine if the two sides of the story merit equal weighting.
"But when we look at the scientific evidence on MMR and autism we find study after study after study says there is no association."
The polite understatement of a government official which barely conceals the frustration about this issue inside the Department of Health.
'Don't blame the media'
Sunday Times columnist Amanda Craig, who examined their evidence when she was writing a column about MMR and autism, says it is Whitehall's own fault.
"Frankly, I wasn't impressed. I didn't think their study is as conclusive as they are claiming.
"It didn't look at nearly enough children for a sufficiently long period of time.
"I don't think this is scare mongering. Many people think that the media is wholly irresponsible, but I actually think it has been quite cautious in this instance."
Despite all this Amanda Craig's children have had the MMR jab. Many others, across the UK have not.