What is already known about this topic? COVID-19 vaccination began in the United States in December 2020, and adults aged ≥65 years were prioritized in early phases. What is added by this report? By May 1, 2021, 82%, 63%, and 42% of adults aged ≥65, 50–64, and 18–49 years, respectively, had received ≥1 vaccine dose. From November 29–December 12, 2020 to April 18–May 1, 2021, the rate ratios of COVID-19 incidence, emergency department visits, hospital admissions, and deaths among adults aged ≥65 years (≥70 years for hospitalizations) to adults aged 18–49 years declined 40%, 59%, 65%, and 66%, respectively. What are the implications for public health practice? The greater decline in COVID-19 morbidity and mortality in older adults, the age group with the highest vaccination rates, demonstrates the potential impact of increasing population-level vaccination coverage.