Beginning the global COVID-19 vaccine rollout 100 days after the virus was sequenced could have saved more than 8 million lives by the end of 2021, most of them in lower-middle-income countries, according to modeling evidence brought together in a new policy brief from the United Nations University Institute for Water, Environment and Health (UNU-INWEH). The authors argue that fair vaccine-sharing rules should be established before the next pandemic, rather than negotiated during the crisis itself.