The medical history series on life-expectancy on iPlayer (
https://www.bbc.co.uk/iplayer/episode/m000w6s5/extra-life-a-short-history-of-living-longer-series-1-1-vaccines) is amazing. Very educational and well worth watching (and how little we've learnt from past experiences)...
How the development and delivery of the smallpox vaccine eradicated the disease.