Vaccination isn't a cure, it's prevention. The eradication of Smallpox is the single biggest achievement in the history of medication, period. It has killed more people then anything else in the history of mankind.
You know the Indians? When the Europeans came across, 90-95% of the population in both North and South America died off due to Smallpox. 90%+.
Without it, we wouldn't have an America. The Indians would've been able to field actual armies, and Cortez wouldn't have been able march off with all the Aztec gold with a few hundred conquistadors. You think it was modern technology that gave Cortez the upper hand? No, it was biological warfare. Imagine three million Aztecs descending on 800 conquistadors and their muskets. Yeah.
Then again, without Smallpox we wouldn't have Islam or Christianity. So, man history has some big fucking butterflies.