Global scarcity of COVID-19 vaccines raises ethical questions about their fair allocation between nations. Section I introduces the question and proposes that wealthy nations have a duty of justice to share globally scarce COVID-19 vaccines. Section II distinguishes justice from charity and argues that beneficiaries of unjust structures incur duties of justice when they are systematically advantaged at others expense. Section III gives a case-based argument describing three upstream structural injustices that systematically advantaged wealthy countries and disadvantaged poorer countries, contributing (...) to global disparities of COVID-19 vaccines. Section IV examines more closely the duties of justice owed, including a duty to relinquish holdings, restitute victims, and restore relationships. Section V concludes that wealthy nations have a duty of justice to share COVID-19 vaccines with poor nations and to restore relationships damaged by injustice. All nations should take steps to transform unjust structures. (shrink)