South Africa’s leader accused developed countries Tuesday of hoarding much-needed coronavirus vaccines at the expense of poorer nations, as a new study warned that unequal access to the doses could cost the global economy trillions of dollars.

Speaking at a virtual meeting of the World Economic Forum, South African President Cyril Ramaphosa called on wealthy nations to release any excess doses “so that other countries can have them.”

“The rich countries of the world went out and acquired large doses of vaccines. . . . Some countries even acquired up to four times what their population needs,” he said.

“We are all not safe if some countries are vaccinating their people and other countries are not vaccinating,” Ramaphosa continued. “We all must act together in combating the virus.”

The president’s remarks came amid growing battles among nations over limited supplies of the most effective vaccines against the coronavirus, which has infected about 100 million people and killed more than 2 million worldwide.

The front-runner vaccines include two developed by U.S.-based companies Pfizer and Moderna, as well as a third from Britain’s AstraZeneca. Russia and China have also both developed vaccines, some of which have reached developed nations, but scientists say a lack of data raises questions about the shots’ efficacy.

In a study released this week, and funded by the International Chamber of Commerce (ICC), researchers said that vaccine inequality among nations could lead to more than $9 trillion in global economic losses, half of which would be borne by advanced economies, even if they vaccinated their entire populations.

Together, Britain, Canada, the United States and the European Union have purchased the lion’s share of the global vaccine supply, according to publicly available data.

“No economy can recover fully from the pandemic until vaccines are equally accessible in all countries,” the Paris-based ICC, a global trade and investment body, said in a statement.

The report calculated that the global gross domestic product loss of not ensuring equal access to vaccines “is higher than the cost of manufacturing and distributing vaccines globally,” which it put at $27.2 billion.

“This is because advanced economies are tightly connected to unvaccinated trading partners, which consist of a large number of emerging markets and developing economies,” the report said. As long as the pandemic is devastating economies in poorer countries, wealthier nations will experience a “non-negligible drag” on their economies, too, the report said.

On Monday, the director general of the World Health Organization, Tedros Adhanom Ghebreyesus, warned against what he called “vaccine nationalism.”

It “might serve short-term political goals. But it’s in every nation’s own medium and long-term economic interest to support vaccine equity,” he wrote on Twitter.

“Until we end the pandemic everywhere, we won’t end it anywhere. As we speak, rich countries are rolling out vaccines, while the world’s least-developed countries watch and wait,” he tweeted. “Every day that passes, the divide grows larger between the world’s haves and have-nots.”

This month, the WHO-supported Covax initiative, which seeks the equal distribution of vaccines worldwide, said that it signed advance-purchase agreements with Pfizer and AstraZeneca for about 180 million doses. Some of them will be available in the first quarter of 2021, the statement said. Afghanistan, however, said it doesn’t expect to receive its first Covax shots for another six months.

In total, Covax said that it is on track to deliver 2 billion coronavirus vaccine doses in 2021, including 1.3 billion doses in 92 lower-income countries.