Unraveling the arc of vaccine progress

The philosopher Thomas Hobbes famously described life in 1651 as "nasty, brutish, and short." He was undeniably correct, with estimates of average life expectancy in the UK at the time ranging from 37 to 40 years, largely owing to a high infant mortality rate. For example, in London, there were an estimated 251 deaths per 1000 live births. The situation was even more dire in the early American colonies, particularly in the Southern colonies, where infectious diseases were rampant. Even as recently as 50 years ago, global infant mortality rates were around 100 deaths per 1000 live births, at a time when fewer than 5% of children in developing countries received even a single vaccine dose.