Xi said China would directly donate 600 million doses to African countries and provide 400 million other shots through “joint production” between Chinese companies and countries in Africa.

“We need to put people and their lives first, be guided by science, support waiving intellectual property rights on COVID-19 vaccines, and truly ensure the accessibility and affordability of vaccines in Africa to bridge the immunization gap,” Xi said from Beijing via a televised speech at the Forum on China-Africa Cooperation in Senegal.

Xi’s speech came hours before U.S. President Joe Biden urged countries around the world to help equalize global COVID-19 vaccine coverage as a means to prevent the emergence of new variants like Omicron.

“We need to do more than vaccinate Americans. To beat the pandemic, we have to vaccinate the world as well, and America’s leading that effort,” Biden said in a speech on Monday. “Now we need the rest of the world to step up.”

Biden said that the U.S. has donated 275 million vaccine doses to over 110 countries. China, meanwhile, has donated 119 million vaccine doses to dozens of countries, according to Bridge Consulting.

But the donations thus far have not been enough to equalize global access to vaccines. High-income nations have distributed more third-dose booster shots than the total number of doses low-income countries have provided to their citizens.

Countries in Africa have felt the brunt of global vaccine inequity. African countries have fully vaccinated just over 7% of their populations, far below the global average of 43%, according to Our World in Data. Europe, Asia, and North America, meanwhile, have fully vaccinated rates of 58%, 55%, and 48%, respectively.

The emergence of the highly mutated Omicron variant of COVID-19 is renewing calls to equalize vaccine access; experts have long cautioned that unvaccinated areas create ripe conditions for the emergence of new variants.

Like all viruses, COVID-19 develops random mutations as it spreads through the population, and some of those mutations can increase its infectiousness or make it more resistant to vaccines. Unvaccinated people are better hosts than vaccinated people for creating more mutations because COVID-19 can spread relatively unfettered through unvaccinated populations compared with vaccinated ones.

“The key to slowing the emergence and spread of new variants will be increased vaccine coverage,” says Ashley St. John, an associate professor of immunology at the Duke-NUS Medical School in Singapore.

The specific mutations in the Omicron variant have raised fears that it may be more resistant to vaccines, and vaccine companies like U.S. pharmaceutical giant Pfizer and Chinese vaccine maker Sinovac each announced this week that they are working on Omicron-specific booster shots. But current vaccine stocks still remain the strongest tool in protecting populations in Africa and around the world against Omicron and other COVID-19 variants.

“Vaccines are very protective against other variants with some of these mutations, so it’s unlikely that the vaccines will be ineffective against Omicron,” says St. John.

Tedros Adhanom Ghebreyesus, director-general of the World Health Organization, said in a speech to the World Health Assembly on Monday that unequal vaccine access remains the most important roadblock in bringing an end to the global pandemic.

“The longer vaccine inequity persists, the more opportunity this virus has to spread and evolve in ways we cannot predict nor prevent,” he said. “We cannot end this pandemic unless we solve the vaccine crisis.”