 This retrospective cohort study analyzed electronic health record, EHR, data from patients with SARS, COV-2 infections hospitalized in participating healthcare systems representing 315 hospitals across six countries, comparing hospitalization rates, severe COVID-19 risk, and mean laboratory values between patients hospitalized during the first and second waves of the pandemic. The results showed that patients hospitalized in the second wave had a significantly lower risk of severe COVID-19 compared to those hospitalized in the first wave, with lower mean values of seriactive protein, CRP, ferritin, fibrinogen, prokalsatinin, de dimer, and creatinine on admission and at the seventh hospital day. The study demonstrated the feasibility and power of harmonizing heterogeneous EHR data from multiple international healthcare systems to rapidly conduct large-scale studies to characterize how COVID-19 clinical trajectories evolve. This article was authored by Griffin M. Weber, Harrison G. Zhang, Sehi Le, and others. We are article.tv, links in the description below.