A plan to save the lives of 10 million children in developing countries has been launched by UK Chancellor Gordon Brown and his European counterparts.
Polio vaccines are among the life-saving measures planned
By raising £2.2bn ($4bn) over 10 years they hope to cut the number of deaths from diseases like measles, polio, hepatitis B, tetanus, and diphtheria.
Illnesses from such immunisable diseases kill millions every year.
Critics fear the scheme, first championed by the chancellor in 2003, is a "buy now, pay later" project.
Bill Gates role
The UK has pledged the equivalent of £70m ($130m) each year - 35% of the money for the International Finance Facility for Immunisation.
Mr Brown said the launch had been made possible by recent long-term commitments from other donor countries.
France has pledged the equivalent of $100m (£54m) a year; Italy $30m (£16m) a year; Spain $12m (£6.5m); and Sweden £27m (£15m).
Microsoft magnate Bill Gates has promised a further $750m (£408m) over 10 years through his Gates foundation.
The scheme, dubbed Iffim, uses long-term financial commitments to provide "frontloaded" resources for the Global Alliance for Vaccine and Immunisation (Gavi).
The extra resources are predicted to save the lives of five million children by 2015 and a further five million after that.
Donors will make payments to Gavi over 20 years from 2006, allowing it raise funds from investing now with the back-up of guaranteed future funding.
Mr Brown said: "By the power of medical advance with a wholly new innovative mechanism to frontload long-term finance, Iffim ... will enable 10 million lives to be saved and spare millions of families the agony of a loved one needlessly dying."
Later, he told BBC News the West could not allow "disquiet, anger and outrage" to breed in developing nations and argued that much of the British public supported increased overseas aid.
Peter Hardstaff, from the World Development Movement, said he wanted to increase funds for immunisation but did not approve of the details of the scheme.
"Our concern is that because the IFF is a way of borrowing money from international financial markets, in years to come we're going to end up using aid money to pay off the interest to financiers rather than helping the poor," he said.
Mr Hardstaff argued it would be better for the schemes to be funded from ordinary government revenue.
Nearly 30 million children go without immunisation each year.
Illnesses from immunisable diseases make up more than half of all illnesses in the poor world - nine times the level in the richest countries.
At the launch, Graca Machel, chairwoman of Vaccine Fund Board, said she hoped nations such as the US would become donors to the IFF.
President George Bush has previously said the IFF plans do not fit with US "budgetary process".