By Jon Cronin BBC News Online business reporter

The Gates' operate a hands-on approach to philanthropy

The decision by the foundation run by Microsoft magnate Bill Gates to give $750m (£400m) to a worldwide infant vaccination programme has been welcomed by immunisation campaigners.

The donation is just the latest in a line of offerings from Mr Gates, one of the world's richest men.

Over the past decade Mr Gates has made a name as one of the world's top philanthropists, with the Bill and Melinda Gates Foundation pledging $7bn to good causes.

Back in July 2004, Microsoft decided to return $75bn (£40.5bn) in cash to the software giant's shareholders.

Mr Gates, Microsoft's billionaire co-founder and the company's biggest shareholder, said he intended to give his estimated $3bn share of the payout to his charitable foundation.

Set up in 2000 by Mr Gates and his wife Melinda from the merger of two family charitable trusts, the foundation has a $27bn endowment and is dedicated to promoting greater equality in global health and learning.

'Unconscionable disparity'

Together with the British-based Wellcome Trust, which holds assets worth around £9bn, the foundation leads the world in charitable giving.

Run by Mr Gates' father, William H Gates Sr, the foundation lists one of its primary goals as "reducing the 'unconscionable disparity' that exists between the way that we live and the way that the people of the developing world live".

Mr Gates' money could help improve the health of millions

In February 2004, the foundation pledged $83m to help fight tuberculosis, a disease which the World Health Organisation says kills nearly 2 million people a year.

In 2003 it donated $168m to fund research into malaria and made $60m available to fund research into how the risk of HIV infection among women in developing countries can be reduced.

Backed by Mr Gates' vast wealth - amassed by building Microsoft into the world's biggest software company - the foundation's operations are driven by the concept of a more businesslike and hands-on approach to philanthropy.

Making an impact

Unlike the Wellcome Trust, a research-funding charity which was established in 1936 following the death of Sir Henry Wellcome, the foundation's set-up enables its benefactor to oversee how his money is being spent.

At last year's World Economic Forum in Davos, Mr Gates told world leaders that he had a duty to ensure his wealth "goes back to global society in the most impactful way".

The Gates' Foundation Endowment of $27bn. $7.1bn in grants since 1994. Largest grant: $1bn to the United Negro College Fund. Average grant: $903,711. Supports work in more than 100 countries.

Since his involvement with the foundation, Mr Gates has become something of a "walking encyclopaedia of medical knowledge", according to Warren E Buffett, the chief executive of financial services firm Berkshire Hathaway.

"I have heard him speak many times on this subject and each time I have been amazed by the breadth of his knowledge," Mr Buffett told Time magazine.

Mr Gates' wife also keeps a close eye on the effectiveness of the foundation's activities, Mr Buffett said.

"Melinda, for her part, travels the world so that she can understand what a cheque from Seattle is actually accomplishing 10,000 miles away."

In terms of assets, the Bill and Melinda Gates foundation dwarfs that of other well-known names in US philanthropy, such as the Rockefeller Foundation or the Ford Foundation.

Long term vision

In language that would not seem out of place in a modern company business plan, the Gates' foundation has pledged to "aggressively pursue a comprehensive approach" in the fight against Aids. "We must marshal the will and resources necessary to develop and distribute an Aids vaccine," Mr Gates has said.

The foundation is also keen to counter criticism that it focuses too much on the trouble facing other countries, and not enough on those in need in its own backyard.

Almost half of the foundation's resources are directed towards domestic US issues, according to Mr Gates.

The foundation's single biggest grant - of $1bn - was awarded to the United Negro College Fund, America's largest minority higher education assistance organisation.

The foundation also promotes access to technology in public libraries and funds groups helping to improve the lives of people in the foundation's own corner of the US, the Pacific Northwest.

Mr Gates has said his long term vision is to improve the lives of millions of people across the globe.