COVID-19 Epidemiology during Delta Variant Dominance Period in 45 High-Income Countries, 2020-2021

The SARS-CoV-2 Delta variant, first identified in Octo-ber 2020, quickly became the dominant variant world-wide. We used publicly available data to explore the relationship between illness and death (peak case rates, death rates, case-fatality rates) and selected predictors (percentage vaccinated, percentage of the population >65 years, population density, testing vol-ume, index of mitigation policies) in 45 high-income countries during the Delta wave using rank-order correlation and ordinal regression. During the Delta-dominant period, most countries reported higher peak case rates (57%) and lower peak case-fatality rates (98%). Higher vaccination coverage was protective against peak case rates (odds ratio 0.95, 95% CI 0.91-0.99) and against peak death rates (odds ratio 0.96, 95% CI 0.91-0.99). Vaccination coverage was vital to preventing infection and death from COVID-19 during the Delta wave. As new variants emerge, pub-lic health authorities should encourage the uptake of COVID-19 vaccination and boosters.