Measuring income-associated inequalities in COVID-19 vaccination on a global scale: a modeling study.

Inequalities in the accessibility and utilization of quality, safe, and effective coronavirus disease 2019 (COVID-19) vaccines across and within countries limited their value in protecting health during the COVID-19 pandemic. We quantified cross-country, income-associated inequality in COVID-19 vaccination using statistical models based on the data for 79 countries through December 2021. We found notable inequality in vaccinations per capita. At least 11.9% of doses administered in high-income countries could be redistributed to low-income countries to substantially reduce income-associated inequality in vaccinations. The results of this modeling study indicate that reliance on multiple doses of vaccine to attain optimal protection from COVID-19 is a significant contributor to inequality in vaccinations per capita. Dose-sharing mechanisms should account for and include efforts to optimize the capabilities of health systems to deliver vaccines.