The international scheme to ensure equal access to COVID-19 vaccines is 140 million doses short because of India's continuing COVID crisis.
The Serum Institute of India the largest single supplier to the Covax scheme, has made none of its planned shipments since exports were suspended in March.
The UN children's agency Unicef buys and distributes vaccines for Covax.
It is urging leaders of G7 nations and EU states to share their doses.
They are due to meet in the UK next month.
Unicef says data it has commissioned suggests that together this group of countries could donate around 153 million doses, while still meeting their commitments to vaccinate their own populations.
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