" The major credit for the decrease in child mortality and the resultant increase in life expectancy must go to the control of disease through public health measures. At first, this took the form of improvements in sanitation and in water supplies. Eventually science caught up with practice and the germ theory of disease was understood and gradually implemented, through more focused, scientifically based measures. These included routine vaccination against a range of diseases and the adoption of good practices of personal and public health based on the germ theory. The "

― Angus Deaton , The Great Escape: Health, Wealth, and the Origins of Inequality