Microsoft founder Bill Gates is to give $10bn (f7.1bn) over the next decade to research new vaccines and bring them to the world's poorest countries.
Calling upon governments and businesses to also contribute, Mr Gates and his wife Melinda said the money will produce higher immunisation rates and help to ensure that 90pc of children are protected against diseases such as diarrhoea and pneumonia in poorer nations.
He told the Davos economic forum: "Vaccines already save and improve millions of lives in developing countries. Innovation will make it possible to save more children than ever before."
He said the commitment more than doubles the $4.5bn (f3.2bn) the foundation he and his wife set up has given to vaccine research over the years.
The foundation said that 7.6m children under five could be saved by 2019 as a result of the donation. Margaret Chan, head of the World Health Organisation, called the contribution unprecedented and urged governments and private donors to add to the initiative.