Background: Because of the increased risk for severe coronavirus disease 2019 (COVID-19), the Advisory Committee on Immunization Practices (ACIP) initially prioritized COVID-19 vaccination for persons in long-term care facilities (LTCF), persons aged ≥65 years, and persons aged 16-64 years with high-risk medical conditions when there is limited vaccine supply. We compared characteristics and severe outcomes of hospitalized patients with COVID-19 in the United States between early and later in the pandemic categorized by groups at higher risk of severe COVID-19.

Methods: Observational study of sampled patients aged ≥18 years who tested positive for SARS-CoV-2 and admitted to one of 14 academic hospitals in the United States during March-June and October-December 2020. Demographic and clinical information were gathered from electronic health record data.

Results: Among 647 patients, 91% met ≥1 of the following risk factors for severe COVID-19 [91% March-June (n=434); 90% October-December (n=213)]; 19% were LTCF residents, 45% were aged ≥65-years, and 84% had ≥1 high-risk condition. The proportion of patients who resided in a LTCF declined significantly (25% vs. 6%) from early to later pandemic periods. Compared with patients at lower risk for severe COVID-19, in-hospital mortality was higher among patients at high risk for severe COVID-19 (20% vs. 7%); these differences were consistently observed between March-June and October-December.

Conclusions: Most adults hospitalized with COVID-19 were those recommended to be prioritized for vaccination based on risk for developing severe COVID-19. These findings highlight the urgency to vaccinate patients at high risk for severe COVID-19 and monitor vaccination impact on hospitalizations and outcomes.

Keywords: COVID-19; SARS-CoV-2; United States; hospitalization; vaccination.