As coronavirus cases continue to spike throughout the U.S., Microsoft founder and public health advocate Bill Gates addressed how a hypothetical vaccine should be distributed. Speaking on Sunday at a remote conference hosted by the International AIDS Society, Gates said that the treatment must be given out first to those most in need and not to those with the money to pay for it.

“If we just let drugs and vaccines go to the highest bidder, instead of to the people and the places where they are most needed, we’ll have a longer, more unjust deadlier pandemic,” Gates explained. “We need leaders to make these hard decisions about distributing based on equity, not just on market-driven factors.”

According to the World Health Organization, as of July 6 there are 21 coronavirus vaccine trials that have progressed to human trials with volunteers. Among these, the ones conducted by Moderna in the U.S., Sinovac Biotech in China, and AstraZeneca in the U.K. are considered to be the furthest along, despite a recent delay for Moderna’s late-stage trials.

Samples tested in humans by the likes of Pfizer and BioNTech have managed to produce immune responses. However, these tests have also led to a number of troubling, but not life-threatening, side effects at higher doses, including fever and trouble sleeping.

“Global cooperation, a resolve to invent the tools and get them out where they’re needed most is critical,” Gates continued. “When we have those things, nations, institutions and advocates working together on this collective response, we do see remarkable impact.”

Through his philanthropic organization, the Bill & Melinda Gates Foundation, Gates has pledged over $250 million for coronavirus research endeavors. This includes vaccine trials, as well as diagnostics, therapies, and programs that aim to lessen the social and economic impacts of the pandemic.