Smallpox killed billions of people on this planet.

You can dispense with the smallpox, allknowing one.

Jenner infected himself with smallpox to test his vaccine.

But smallpox eradication was hard it was very, very hard.

Well, that scar on her upper arm is from a smallpox vaccination.

Here we come down with the eradication of smallpox, better education, health service.

If they didn't, we wouldn't have cures for yellow fever, polio and smallpox.

Because I thought that had been eradicated in the way that smallpox had been eradicated.

But the third challenge we have and probably even bigger one, the biggest challenge is that, in contrast to smallpox where you could always see your enemy every single person almost who was infected with smallpox had this telltale rash.

You can see, with independence, literacy improved and vaccinations started, smallpox was eradicated, hygiene was improved, and things got better.

They point to the successes of aid the eradication of smallpox, and the distribution of tens of millions of malaria bed nets and antiretrovirals.

But when was the last time you worried about smallpox, a disease that killed half a billion people last century and no longer is with us?

So you can't see the enemy most of the time, and as a result, we've needed a very different approach to eradicate polio than what was done with smallpox.

The second challenge we had was in contrast to the smallpox vaccine, which was very stable, and a single dose protected you for life the polio vaccine is incredibly fragile.

One congressman here in the United States thinks that the entire investment that the U.S. put into smallpox eradication pays itself off every 26 days in foregone treatment costs and vaccination costs.

The first is that, when we started trying to eradicate polio about 20 years ago, more than twice as many countries were infected than had been when we started off with smallpox.