Dec. 24, 2020 In mid-December, before a key vote by an advisory panel for the Centers for Disease Control and Prevention, a public debate flared up over what might well be the most momentous policy decision of 2021: how to distribute the Covid-19 vaccine. This particular fight centered on how to balance the vaccination of seniors (who die from the coronavirus at much higher rates than younger people) against that of essential workers (who, because they come into contact with many people over the course of any given day, risk getting sick themselves and becoming superspreaders). That debate was just the first of what will be many contentious ones in the months to come, when supplies of Covid vaccine will surely be among the world’s most precious, scarce resources. The calculation of how to prioritize various groups inevitably touches on all the fault lines that divide American society — race, class, age, geography, occupation and more — and ultimately bleeds into the question of our ethical obligations to the poorer nations of the world, which risk being forced to wait for lifesaving vaccine supplies while the wealthy save themselves first.