Forbes' Matthew Herper provides a cover story on Bill Gates' multibillion-dollar effort to change the world with a new generation of cheap vaccines that will save millions of lives. And Gates is bringing the same rigid discipline that helped make Microsoft a global powerhouse. "The metric of success is lives saved, kids who aren't crippled," Gates tells Herper. "Which is slightly different than units sold, profits achieved. But it's all very measurable, and you can set ambitious goals and see how you do." Story