Given the scarcity of safe and effective COVID-19 vaccines,a chief policy question is how to allocate them among different sociodemographic groups.This paper evaluates COVID-19 vaccine prioritization strate-gies proposed to date,focusing on their stated goals;the mechanisms through which the selected alloca-tions affect the course and burden of the pandemic;and the main epidemiological,economic,logistical,and political issues that arise when setting the prioritization strategy.The paper uses a simple,age-stratified susceptible-exposed-infectious-recovered model applied to the United States to quantitatively assess the performance of alternative prioritization strategies with respect to avoided deaths,avoided infections,and life-years gained.We demonstrate that prioritizing essential workers is a viable strategy for reducing the number of cases and years of life lost,while the largest reduction in deaths is achieved by prioritizing older adults in most scenarios,even if the vaccine is effective at blocking viral transmission.Uncertainty regarding this property and potential delays in dose delivery reinforce the call for prioritizing older adults.Additionally,we investigate the strength of the equity motive that would support an allo-cation strategy attaching absolute priority to essential workers for a vaccine that reduces infection-fatality risk.