Bill and Melinda Gates have announced they are pledging $10bn (£6.2bn) over 10 years to provide vaccines for the world's poorest countries.
Bill Gates' wife Melinda visits hospital patients in Benin, north Africa
Child mortality could be significantly reduced if governments and the private sector spent more money developing vaccines, the couple said at the World Economic Forum's annual meeting.
"We must make this the decade of vaccines," Mr Gates said.
"Vaccines already save and improve millions of lives in developing countries. Innovation will make it possible to save more children than ever before."
Delivering 90% more vaccines - including new ones to prevent severe diarrhoea and pneumonia - could prevent the deaths of some 7.6 million children under five over the next 10 years, according to the Gates Foundation.
Microsoft founder Bill Gates and his wife Melinda
Mrs Gates described vaccines as a miracle.
She said: "With just a few doses, they can prevent deadly diseases for a lifetime.
"We've made vaccines our number-one priority at the Gates Foundation because we've seen first hand their incredible impact on children's lives."
If additional vaccines are developed and introduced in this decade - such as for tuberculosis - even more lives could be saved.
The new funding announced is in addition to the $4.5bn (£2.8bn) that the Gates Foundation has already committed to vaccines since its inception.