The money will finance immunisation schemes in 72 countries in an attempt to eradicate lethal diseases including polio, hepatitis B, measles, diphtheria, yellow fever and tetanus.
Ten million children die every year from preventable diseases and 30 million go without immunisation. Illnesses from such diseases make up more than half of all those in the poorest countries - nine times the level in the richest nations. The fund should save five million children's lives by 2015.
Britain will contribute $130m a year to the fund for 20 years, about a third of the total. France, which will pay $100m a year, Italy, Spain and Sweden have made firm commitments to the British-led initiative. Their long-term pledges will allow the aid to be "front-loaded" through the purchase of bonds, speeding up the programme by years.
The "spend now, pay later" scheme, or International Finance Facility (IFF), is Mr Brown's flagship to help the developing world. He hopes it will eventually be followed by a wider aid programme but the US has opposed this funding mechanism, saying a US administration cannot commit a future one to spending.
Although the US declined to back the immunisation fund, Bill Gates, the chairman of Microsoft, is to plough $750m into it over 10 years. The money will go through Global Alliance for Vaccines and Immunisation (Gavi), which five years ago brought together Unicef, the World Health Organisation, the World Bank, aid agencies and vaccine manufacturers. More than 78 million children have been immunised and more than a million deaths averted.
Hailing the breakthrough in his long battle to set up an IFF despite US hostility, Mr Brown will say: "What medical advance has made possible, financial stringency and the absence of creative thinking of long-term finance has frustrated.
"Now, by matching the power of medical advance with a wholly new innovative mechanism to front-load long-term finance, the IFF for immunisation which we are launching here today will enable 10 million lives to be saved and spare millions of families the agony of a loved one needlessly dying."
Graça Machel, the wife of Nelson Mandela, who chairs the fund, said: "Gavi and the Vaccine Fund have shown that immunisation saves children's lives. This will provide long-term predictable funding that is urgently needed to save the lives of millions more. This turns promises into action."
Mr Gates said: "The commitments provide a major boost to Gavi's work to ensure that all children have access to life-saving vaccines. I commend... Gordon Brown for his tireless work to make this possible."
The programme is being launched ahead of next week's UN summit in New York. A survey by the charity ActionAid International of 340,000 poor people in 18 countries found that in 64 per cent of the villages visited people regularly went hungry; in 83 per cent, work was not available for part of the year and nearly half had no access to any social services. Women often subsisted on less than half the wages paid to men; children as young as five worked for money in 71 per cent of the villages and four out of five school-age girls have never been inside a classroom.
A family devastated by tetanus and polio
Nurmala Sarkiyah lives with her husband and six children in Sungai Asam, Indonesia. Two of her children have been left disabled by diseases that have been almost totally eradicated in developed countries, thanks to vaccination. Ms Sarkiyah said: "My daughter is disabled after she got tetanus. She went to hospital for three months. She had white spots in her eye when she returned. They got bigger and her eye watered, then it went black. Now she's blind in that eye and also mute."
Thenher two-year-son was struck down by polio. "He had a fever and his arm went stiff," she said. "Then the right side of his body degenerated."
The only aid organisation in the area is Save the Children. Anne Taylor, of the charity, said: "About 30,000 children under the age of five die every day and two-thirds of these deaths could be prevented by having free health services."