Bill and Melinda Gates have announced one of the biggest charitable donations in history – an unprecedented $10bn (£6.24bn) investment in vaccines for children in poor countries over the next decade.

Speaking at the World Economic Forum in Davos, the Microsoft founder called for "a decade of vaccines" to reduce child mortality dramatically by 2020. The money will save an estimated 8 million lives, the couple say. It will pay for a big push to step up coverage of existing vaccines, such as for diphtheria, tetanus and whooping cough, and new ones for pneumonia and diarrhoeal diseases, which are big killers of small children.

The Gates Foundation has made child immunisation the cornerstone of its work in the developing world. "Vaccines are a miracle – with just a few doses, they can prevent deadly diseases for a lifetime," said Melinda Gates. "We've made vaccines our number one priority at the Gates Foundation because we've seen first hand their incredible impact on children's lives."

The biggest charitable donation in history was from Warren Buffett, at the time the second wealthiest man in the world after Bill Gates, and the Gates Foundation was the recipient. Buffet gave $30 billion to help the foundation's work in the developing world.

Bill and Melinda Gates have already committed a total of $4.5bn to the research, development and delivery of various vaccines. They have shown great interest in scientific and technological solutions to the problems of disease and development.

The couple also fund work towards an Aids vaccine, which is still a long way off. Big progress has been made in other disease areas, however. Last week the New England Journal of Medicine published the results of two studies, one in Mexico and the other in Africa, that showed a vaccine against rotavirus was effective not only at reducing cases of severe diarrhoea in under-fives but also cut deaths.

The foundation is also following a malaria vaccine that is in late stage trials in Africa. Results look as though it will be only 50-60% effective, but that could still save many thousands of lives on the continent.

Scaling up existing vaccine coverage in the developing world, plus pneumonia and rotavirus vaccines, to 90% will prevent 7.6 million deaths between 2010 and 2019, the foundation estimates. It says introducing the malaria vaccine from 2014 could save an additional 1.1 million children.

The $10bn will go to the Global Alliance for Vaccines and Immunisation (GAVI), launched at Davos 10 years ago to find finance for vaccination programmes in developing countries. It has reached 257 million additional children with new and underused vaccines so far, which it estimates will prevent 5 million deaths. It will focus on introducing rotavirus and pneumonia vaccines. GlaxoSmithKline, the British company researching the malaria vaccines, said it hoped GAVI would arrange a financing package once the trials were complete. Its chief executive, Andrew Witty, has pledged to take only a minimal profit, to be reinvested in malaria research.

[Since this article was published, GAVI has contacted the Guardian to say that the $10bn will not all be channelled through GAVI. The original foundation announcement that the money would go to vaccines covered research and development, production and delivery. GAVI noted that it deals with delivery only, and does not yet know what funds will be dedicated to this.]

So the Foundation would need to break it down, but frankly I don't think they have begun to break it down yet.

Although Bill and Melinda Gates's donation is huge, they and others have stressed that billions more are needed to step up vaccinations in poor countries to a level where all children will get the protection they need.

"The Gates Foundation's commitment to vaccines is unprecedented but just a small part of what is needed," said Margaret Chan, director general of the World Health Organisation. "It's absolutely crucial that both governments and the private sector step up efforts to provide lifesaving vaccines to children who need them most."

• This article was amended on 1 February and 3 February 2010. The original referred to diptheria. This has been corrected. The article has been updated with a later clarification from GAVI about its share of the $10bn donation.