A global immunisation campaign to save the lives of two to three million children a year in the developing world will be launched next year by a $4bn (£2.2bn) a year vaccination project backed by Britain, France and Bill Gates, the multibillionaire founder of Microsoft.
Government-backed bonds will be floated on financial markets to fund the programme, designed to tackle easily preventable diseases.
Treasury sources said the proposal was at an advanced stage and would be unveiled in the first half of next year, when Britain intends to make Africa the focal point of its presidency of the G8 industrial countries.
Britain was approached by the Global Alliance for Vaccines and Immunisation (Gavi) - an umbrella body covering governments, NGOs and private sector organisations - to see if it would back a plan to frontload extra cash into health programmes.
Mr Brown believes the plan is "an innovative proposal" that could speed up the flow of drugs to tackle diseases such as tetanus, measles, polio, diphtheria, pertussis (whooping cough), hepatitis B, yellow fever and rotavirus (gastroenteritis). The chancellor also sees it as a pilot for his proposed International Finance Facility, a plan to double global aid to $100bn a year through the sale of bonds.
"If, through these means, resources available to immunisation could be scaled up significantly, we have the opportunity to avert two to three million vaccine-preventable deaths every year, especially considering the new vaccines becoming available in the near future."
Treasury officials said the chancellor had discussed the project with Mr Gates, who has pledged part of his personal fortune to the immunisation campaign. The British and French governments, with the World Bank, Gavi and the Bill and Melinda Gates Foundation, are now working out the final details. "Bill Gates is a big supporter," one source said. "This is going to be a public-private partnership.
The proposal is to float 15-year government-backed bonds in the world's capital markets. There would be two five-year disbursement phases followed by a five-year period in which those who bought the bonds would be repaid.
Goldman Sachs has been working on the financial details of the plan and the City solicitors Linklaters have been handling the legal arrangements.
The Treasury expects that pledges of $400m a year in private and public money could generate 10 times that amount by bond sales.
Investors would have confidence in the investment because they would be guaranteed by governments.
Gavi estimates that 10 million children under the age of five die every year, and believes that immunisation is vital if the UN is to meet its target of cutting infant mortality by two-thirds by 2015.
"Two to three million children die of vaccine-preventable diseases every year," it said.
"If 95% of children in the poorest countries were to be immunised with existing, and new vaccines by 2015, up to 2 million children could be saved every year."
Gavi said the extra money would be spent on effective programmes in 56 low-income countries and on providing more affordable vaccines in middle-income states.
In a four-pronged strategy, it would strengthen healthcare systems in poor countries so they could reach the 25% of children not covered by vaccination programmes.
It would also embark on a long-term programme of buying new and under-utilised vaccines, launch campaigns to provide nationwide immunity, and stockpile oral polio vaccine for an attempt to eradicate the disease.
