ABSTRACT
Inequity in the access to and deployment of the coronavirus disease 2019 (COVID-19) vaccines has brought about great challenges in terms of resolving the pandemic. Aiming to analyze the association between country income level and COVID-19 vaccination coverage and explore the mediating role of vaccination policy, we conducted a cross-sectional ecological study. The dependent variable was COVID-19 vaccination coverage in 138 countries as of May 31, 2021. A single-mediator model based on structural equation modeling was developed to analyze mediation effects in different country income groups. Compared with high-income countries, upper-middle- (ß = -1.44, 95% CI: -1.86--1.02, p < 0.001), lower-middle- (ß = -2.24, 95% CI: -2.67--1.82, p < 0.001), and low- (ß = -4.05, 95% CI: -4.59--3.51, p < 0.001) income countries had lower vaccination coverage. Vaccination policies mediated 14.6% and 15.6% of the effect in upper-middle- (ß = -0.21, 95% CI: -0.39--0.03, p = 0.020) and lower-middle- (ß = -0.35, 95% CI: -0.56--0.13, p = 0.002) income countries, respectively, whereas the mediation effect was not significant in low-income countries (ß = -0.21, 95% CI: -0.43-0.01, p = 0.062). The results were similar after adjusting for demographic structure and underlying health conditions. Income disparity remains an important cause of vaccine inequity, and the tendency toward "vaccine nationalism" restricts the functioning of the global vaccine allocation framework. Stronger mechanisms are needed to foster countries' political will to promote vaccine equity.