Before the 1800s, between 40% and 50% of children in Europe died before their 15th birthday. Now, in Britain that number is well below 1%, according to the UN.
Scientists broadly agree that vaccines were key to this improvement.
“Along with clean water and sanitation, immunisations have had a profound impact on keeping children alive,” says Ben Kasstan-Dabush, a lecturer in global health policy at the University of Edinburgh.
And that’s why some find it so worrying that Britain’s rates have slipped. Last year alone saw measles outbreaks in parts of Birmingham, Bristol, and north London; so far this year, two children in England have died of the disease.
In January, MPs on the Health Committee described the backslide as “national disgrace”.
Some blame the rise of misinformation on social media. Last year, a group of American scientists found that reading just one anti-vax Facebook comment about the HPV jab – given to teenagers – was enough to make some parents hesitate.
But all of the public health experts who spoke to the BBC said that whilst anti-vax social media sentiment plays its part, they don’t think it’s the main reason immunisation rates have slipped.
Instead, they point to something more mundane: they think that parents of young children simply have fewer face-to-face contacts with medical professionals than they did 10 or 15 years ago.