The fear is that Trump will be content with allowing the race to develop and distribute the vaccine to devolve into a global contest — and that poorer countries will be left behind in the rush to procure doses. In essence: that the president’s “America First” view of world affairs as an atavistic scramble for power will lead to unnecessary suffering and death.

“The worst situation would be, if when these tools are available, they go to the highest bidder — that would be terrible for the world,” said Melinda Gates, who, along with her tech entrepreneur husband, Bill, leads a powerful foundation that has devoted billions to health research. “Covid-19 anywhere is Covid-19 everywhere. And that’s why it’s got to take global cooperation.”

The ongoing global scramble for masks, gloves and other personal protective gear offers a harrowing and potentially instructive example. Now imagine, officials and experts say, a similar competition to obtain vaccine doses: It could drag out the health crisis by letting the virus spread for longer than it otherwise might, devastating the very countries least equipped to fight it.