London - Gavi, the global vaccines alliance, says it is committing up to $300m to buy Ebola vaccines and is ready to begin procurement as soon as the World Health Organisation recommends one for use.
As much as $90m more could also be made available to help affected countries introduce the vaccines and to rebuild their health systems, it added.
Clinical trials with experimental shots are now underway as experts race to contain an epidemic that has killed more than 6 000 people in West Africa, though there is still uncertainty over how well they will work and how many doses are needed.
Vaccine to halt pandemic
Experts believe millions of doses of vaccine may be needed both to help end the current epidemic and to contain future outbreaks.
But paying for safe and effective Ebola vaccines is a challenge, since the worst affected countries of Sierra Leone, Liberia and Guinea are some of the world's poorest, providing little commercial incentive for manufacturers.
The money now earmarked by Geneva-based Gavi will help bridge the gap and is expected to be enough to procure up to 12 million courses of vaccine.
In addition to supporting the use of vaccines in the current epidemic, the money could also be used to create stockpiles of Ebola vaccines, similar to those that exist for yellow fever, meningitis and cholera.
Awaiting green light
Gavi, which was set up in 2000 with private and government donor backing, has a track record of bulk-buying vaccine supplies from manufacturers at a low price for the developing world. Since 2000, around 440 million children have been immunised against a range of diseases through Gavi-backed programmes.
Gavi said its board had decided to prepare for procuring Ebola vaccines while still awaiting a green light for the first product "in light of the seriousness of the situation and the risks associated with delays in making a vaccine available".
Two vaccines - one from GlaxoSmithKline and a rival shot from NewLink and Merck - are already undergoing human trials and third one, made by Johnson & Johnson, is about to enter clinical testing.
Gavi said it would meet the funding needs of the Ebola vaccine programme using a combination of existing and new financing. It also plans to join forces with other initiatives that have already pledged funding to address the Ebola crisis.