It is a potentially fatal disease caused by infection with the measles virus. It is most common in children aged 1 to 4, but you can catch it at any age. It is highly infectious, with 90 per cent of those who have not been immunised catching it if they live in the same house as someone with measles.

What are the symptoms?

Around 10 days after infection, a blotchy rash appears, with other symptoms including fever, irritability, runny nose, red eyes, vomiting and coughing. Complications include breathing difficulties, ear infections and brain damage. The most serious complication is a slowly progressive brain infection that starts with intellectual impairment, seizures and eventually death. Measles kills one in 100,000 people who get it.

How common is measles?

One million children die from the disease worldwide each year. In the UK, before immunisation there were around 300,000 suspected cases and up to 20 deaths each year. Since the MMR vaccination was introduced in 1988, the confirmed cases have fallen to around 100 each year.

Which countries use the MMR jab?

MMR is used in all developed countries, except Japan, which uses single jabs. The World Health Organisation says vaccination coverage for measles needs to be 95 per cent to ensure no outbreaks. In the UK coverage has fallen to 85 per cent.