The widening gap for vaccine supplies between rich and poor countries led both South African President Cyril Ramaphosa and World Health Organization chief Tedros Adhanom Ghebreyesus to lash out at “vaccine nationalism.”

Ramaphosa told the WEF that low- and middle-income countries were being shouldered aside by wealthier nations able to acquire “up to four times what their population needs.”

But it warned that the world economy continued to face “exceptional uncertainty” and new waves of COVID-19 infections and variants posed risks, and global activity would remain well below pre-COVID-19 projections made one year ago. IMF chief economist Gita Gopinath said U.S. President Joe Biden’s pledge to fund the World Health Organization’s COVAX vaccine initiative marked “a very big step” to containing the pandemic and ensuring more equitable distribution of vaccines.

“Much more will be needed, because as we can see, given the mutating virus, that this is not a problem that’s going away anytime soon,” Gopinath told a news conference. “There is still a tremendous amount of uncertainty,” she told Reuters in a separate interview. “We know that the health crisis is not over until it’s over everywhere.”

AstraZeneca, however, said in a statement on Tuesday that all of its vaccine supply “at this moment” is only available to governments and multilateral organizations around the world. “It is not possible to make vaccines available to the private sector,” it said. Several companies denied reports that they had joined the initiative, including hospital group DASA SA, which said in a statement it is seeking to understand the commercial availability of vaccines through its suppliers.