Vaccines work! Two sisters, one vaccinated for smallpox, the other was not.

Two sisters, both exposed to smallpox from the same source. The woman on top, aged 21, was vaccinated as an infant. The girl on the bottom, 15 years old, was not. You can see that the vaccine did not eradicate the disease – the woman on top has a couple of lesions. But it’s clear you’d rather be her than her sister.