If you have ever taken a stroll through an old graveyard, you may have winced at the surprising number of tombstones bearing witness to the young age of their occupants. In the past, around 1 in 3 children died before their fifth birthday. It was common for children to perish from diphtheria, measles or whooping cough, to be paralysed by polio or to be born deaf and blind from congenital rubella.
Now fewer than 1 in 150 children die before age 5 in developed countries. Much of this is down to better sanitation and nutrition, but a large part of the credit must also go to vaccines. Despite this, some parents are refusing to allow their children to be vaccinated out of fear that certain vaccines cause autism, or that combined vaccines against several diseases overload the immune system.