Because of the aggressive campaign, it's expected that the last cases of polio seen in the wild will happen sometime in the next two to three years. The World Health Organization is so confident about this that it actually has what's called the Polio Eradication and Endgame Strategic Plan, a strategy on how to make the world polio-free by 2018.
That's extraordinary. This has only happened once before in history, when smallpox was eliminated in 1977. Smallpox killed hundreds of millions of people, and now it's gone, wiped clean off the face of the planet.
Why? Again: vaccines.
This is why I consider vaccines to be one of the very best medical health innovations in human history, if not the best.