Cow pus. It all started with cow pus, nearly 220 years ago.
For more on vaccines: http://www.vox.com/2015/2/10/8007571/vaccine-myths
Subscribe to our channel! http://goo.gl/0bsAjO
Vox.com is news website that helps you cut through the noise and understand what's really driving the events in the headlines. Check out http://www.vox.com to get up to speed on everything from Kurdistan to the Kim Kardashian app.
Check out our full video catalog: http://goo.gl/IZONyE
Follow Vox on Twitter: http://goo.gl/XFrZ5H
Or on Facebook: http://goo.gl/U2g06o
Credit:
Words by: Julia Belluz
Produced by: Estelle Caswell
