A large number of poorer countries receiving Covid-19 vaccines through a global sharing scheme do not have enough doses to continue programmes, the World Health Organization has said.
WHO senior adviser Dr Bruce Aylward said the Covax programme had delivered 90 million doses to 131 countries.
But he said this was nowhere near enough to protect populations from a virus still spreading worldwide.
The shortages come as some nations in Africa see a third wave of infections.
On Monday, South African President Cyril Ramaphosa called for an end to vaccine hoarding by wealthier countries as his government scrambled to curb a steep rise in cases.
On a continental level, only 40 million doses have been administered so far in Africa - less than 2% of the population, Mr Ramaphosa said.
To address this, he said his government was working with Covax to create a regional hub to produce more vaccines in South Africa.
Covax was created last year to ensure Covid-19 doses were made available around the world, with richer countries subsidising costs for poorer nations.