To evaluate the hospital-level impact of the COVID-19 pandemic on U.S. academic medical centers (AMCs) and assess regional variation in care delivery to inform public health emergency preparedness strategies.

We retrospectively analyzed adult inpatient discharges from 106 AMCs using Vizient® Clinical Data Base from October 2019 to December 2023. The study period was divided into pre-COVID (Oct 2019-Mar 2020), early-COVID (Apr 2020-Dec 2020), late-COVD (Jan 2021-May 2023), and post-COVID (Jun-Dec 2023). Outcomes included hospital encounters, length of stay (LOS), ICU admissions, ICU LOS, mortality, and case mix index (CMI). Mixed models assessed temporal and regional variation.

Among 13.5 million discharges, monthly encounters declined during early COVID and rebounded post-COVID (P < 0.0001). Observed LOS increased from 6.2 to 6.7 days during the pandemic and remained elevated post-COVID (P < 0.0001). ICU LOS rose during early and late COVID (P < 0.0001), while ICU admission rates declined slightly over time (P = 0.0112). Mortality peaked at 3.4% during early COVID and returned to 2.8% post-COVID (P < 0.0001).

The COVID-19 pandemic significantly disrupted inpatient operations at U.S. AMCs, with increased LOS, ICU burden, and case complexity. By segmenting the pandemic into phases, we identified patterns in hospital performance that reflect evolving public health challenges.