Under “Operation Warp Speed,” the Trump administration hopes to have 300 million doses of vaccine ready for domestic use by January 2021. That outcome would largely satisfy domestic needs in the United States, experts say, but it would mean prioritizing low-risk individuals in one the world’s richest countries over high-risk health care workers and other vulnerable populations elsewhere in the world.

Such concerns prompted more than 140 world leaders and other dignitaries on Thursday to sign an open letter to all governments demanding that Covid-19 vaccines be considered a “global good” to be shared equitably. The letter came just a day after Paul Hudson, CEO of pharmaceutical giant Sanofi, angered the French government by indicating the U.S. would have first access to his company’s output.

“I do think that there’s a significant risk, at least under the current plan, that the U.S. will vaccinate not only health workers and high-risk populations and priority populations for breaking transmission chains, but also low-risk individuals first,” said Tom Bollyky, director of the global health program at the Council on Foreign Relations.