Prime Minister Boris Johnson is ordering urgent action to ensure that children and young people in Britain are protected against measles.
The disease can be stopped through two doses of the MMR vaccine, but immunisation rates have been falling for a number of reasons.
And the UK has lost its measles-free status, three years after the virus was eliminated in the country. In the first quarter of 2019, there were 231 confirmed cases in the UK.
Many of the UK cases were acquired abroad with some onward spread in under-vaccinated communities.
Just 87% of UK children are receiving their second dose, which is below the 95% target for measles elimination.