Universal Health Coverage and Preparedness Payoffs: Global COVID-19 Vaccination Rates

<b>Objective</b>: The pandemic exposed global inequities in terms of health system capacities and vaccination coverage. This study evaluated the relationship between countries' preparedness and COVID-19 vaccination rates. <b>Methods</b>: In this ecological study, we gathered global pre-pandemic data on country-level States Parties Self-Assessment Annual Reporting (SPAR) and universal health coverage (UHC) indexes. We then analyzed their relationship with COVID-19 vaccination rates in 2021-2022, using bivariate and multivariate analyses, including confounders, such as the country's income classification and population demographics. <b>Findings</b>: The mean vaccination rates increased from 32.2% in October 2021 to 51.2% by August 2022. The UHC and SPAR indexes showed strong positive correlations with vaccination rates (r = 0.76 and r = 0.66, respectively, <i>p</i> < 0.001). In regard to the multivariate analyses, both the UHC (B = 0.81, 95% CI: 0.56-1.06) and SPAR (B = 0.34, 95% CI: 0.19-0.49) indexes remained significant predictors of vaccination rates, even after adjusting for country income level, with their influence strengthening over time, while income level effects diminished. <b>Conclusions</b>: This study underscores the critical importance of preparedness efforts, as gauged by the SPAR and UHC indexes, in shaping the effectiveness of COVID-19 vaccination responses globally. Strengthening preparedness measures is important for optimizing vaccination strategies and achieving broader immunization coverage targets.