Bill Gates, Britain and other nations commit funds to help treat preventable diseases among world's poorest children.
Donors from around the world have pledged $4.3bn for a programme that aims to vaccinate 250 million of the world's poorest children against lifethreatening diseases.
The pledges surpassed the $3.7bn target set by the Global Alliance for Vaccines and Immunisation (GAVI), which says it could prevent more than 4 million premature deaths by 2015.
"We have exceeded the figure that we set ourselves and we have received firm pledges for a sum of $4.3bn," Andrew Mitchell, Britain's International Development Secretary announced at the end of the conference in London on Wednesday.
Britain and Bill Gates, the Microsoft chairman jointly committed $2.3bn to help vaccinate more than 80 million children in impoverished countries.
David Cameron, Britain's prime minister, said the $1.3bn donated by his country would help save 1.4 million lives over the next five years.
"Today we come together because we have the chance to save another four million lives in four years," he said.
"Frankly the idea of children dying from pneumonia and diarrhoea should be absolutely unthinkable in 2011.
"But for many parents in the developing world it is a devastating reality."
Gates, a billionaire and philanthropist who helped set up the alliance, said his charitable foundation would commit an additional $1bn over five years.
"It's not every day you give away $1bn but for a cause like this it's exciting to be doing this," he said.
Their announcements came a day after Kevin Rudd, Australia's foreign minister, said his country would commit $211m to GAVI.
"What I see across the international community is a growing commitment to vaccinations ... as one of the most effective forms of aid delivery," Rudd told the Reuters news agency. "This is a good investment."
GAVI, a non-profit organisation which funds bulk-buy vaccination programmes for poor nations that cannot afford Western prices, is seeking an extra $3.7bn in funds to prevent four million child deaths by 2015 with immunisation campaigns reaching more than 240 million children.
The alliance has already vaccinated 288 million children in 19 countries, but wants to extend the vaccination programme to another 26 countries
Pneumonia and diarrhoea kill three times as many children under the age of five as HIV/AIDS even though vaccines are available to prevent such deaths.
Many developing countries cannot afford the vaccines.