OXFORD - Although the Bill & Melinda Gates Foundation is adding $6 billion to its fund for global health care development, the impact of the foundation's attempts to spur vaccine development and its creation of a trust to purchase vaccines for the developing world may be hard to predict.

According to the foundation, contrary to some reports last week, the bulk of the money has yet to be allocated and there has been no decision on such a trust. Still, the foundation believes it has found charitable initiatives capable of inducing the development of vaccines for diseases for which there have been limited markets - either because the markets are too small or because the potential beneficiaries lack the funds to pay.