The Bill & Melinda Gates Foundation pledged $10 billion over the next ten years to help research, develop and deliver vaccines for the world's poorest countries.

The Gateses said that increased investment in vaccines by governments and the private sector could help developing countries dramatically reduce child mortality by the end of the decade — averting more than 8 million deaths annually by 2020.

"We've made vaccines our number-one priority at the Gates Foundation," said Melinda Gates.

Since the last century, smallpox has been eradicated, polio is on the verge of being eradicated and more than 2 million deaths are averted each year.

"We must make this the decade of vaccines," said Bill Gates. "Vaccines already save and improve millions of lives in developing countries. Innovation will make it possible to save more children than ever before."

By significantly scaling up the delivery of life-saving vaccines in developing countries to 90 percent coverage—including new vaccines to prevent severe diarrhea and pneumonia—the model suggests that we could prevent the deaths of some 7.6 million children under 5 from 2010-2019. The foundation also estimates that an additional 1.1 million children could be saved with the rapid introduction of a malaria vaccine beginning in 2014, bringing the total number of potential lives saved to 8.7 million.

If additional vaccines are developed and introduced in this decade—such as for tuberculosis—even more lives could be saved.

Bill and Melinda Gates made their announcement Friday at the World Economic Forum's Annual Meeting in Davos, Switzerland. The new funding is in addition to the $4.5 billion that the Gates Foundation has already committed to vaccine research, development and delivery to date across its entire disease portfolio since its inception.