It's hard to miss news reports about the three-in-one Measles, Mumps and Rubella (MMR) vaccine, which has some parents worried. The media is saturated with stories about a controversial study, which links the MMR jab with autism and a bowel disorder, and anecdotal evidence from parents who say their children became ill after they were immunised.
Uptake of the vaccine has started falling in the UK, which increases the risk that the viruses will spread.
But do parents really need to worry about the MMR jab? Why is this happening, who's at risk, and how dangerous are infections like Measles anyway?
Richard Hammond, the presenter of Should I Worry About...?, has personal reasons to be interested in the jab. His youngest daughter is due to be immunised and he and his wife, Mindy, don't know what to do.
Richard learns from Professor David Goldblatt at the Institute of Child Health at Great Ormond Street Hospital for Children in London that children can die from Measles, a preventable disease, and if enough children aren't immunised, there could be an epidemic.
Professor Goldblatt tells him that if between 20-30% of children don't get the jab, the viruses can spread more easily. He says that children who can't get immunised for health reasons are particularly at risk. For example, kids who are being treated for cancer often can't get the jab. They depend on all the other children getting their jabs. If they catch Measles, Mumps or Rubella, the consequences can be very serious because their immune systems are already weakened.
Healthy children are also at risk from these diseases.
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Professor Goldblatt tells Richard that there is "no doubt" that the MMR jab is safe, a claim that he says is supported by numerous studies.
He says that the cause of most of the worry, a scientific paper that appeared it the Lancet in 1998, is questionable because other researchers haven't been able to repeat the findings.
It's one of the basic principles of science that it should be possible to repeat a study and get the same results.
Richard takes this information to heart and knows he must have his daughter immunised, but he can't forget the worrying headlines.
An alternative to the MMR jab that is available to all parents, if they pay, is single doses of the different vaccines. Children can get Measles, Mumps and Rubella vaccines separately.
Richard speaks to Dr Tim Davey who offers the separate vaccine injections. He says he does this to set worried parent's minds at rest, but warns that there are risks and drawbacks to having the jabs separately.
Dr Davey tells Richard that "if there's a mistake to be made, it's not vaccinating".
In the end, Richard and his wife decide on the single jabs for their daughter.
A matter of trust
In talking to parents, Richard comes to the conclusion that many parents don't trust government health advice, even when nearly all the scientific evidence backs up their claims. The parents say they're not listened to and don't get all the information that's available.
Richard speaks to Shereen El Feki, a journalist at the Economist who specialises in health care, business and science. El Feki tells Richard that "rightly or wrongly the public is wary of government advice" and the advice of big institutions in general.
El Feki makes it clear that this isn't a new problem and concerns all governments – past, present and possibly future.
El Feki says that in the last decade there has been "a push to involve the public in decision making", and therefore it shouldn't be a surprise that people are questioning public policy.
El Feki's advice to politicians is to be open about how they reach decisions, and not be afraid to admit that many issues have no simple, "black and white" solution.
Richard consults with parents up and down the country, and he helps them draw up a message detailing their concerns. They project their message onto the Houses of Parliament with light to get the attention of the country's lawmakers from all political parties.
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