Outcomes

For the propensity score–matched cohort study, the primary outcome was hospitalization or death by 28 days. Secondary outcomes included the 28-day hospitalization rate and 28-day mortality rate.

For the randomized comparative effectiveness trial, the primary outcome was hospital-free days up to day 28 after mAb treatment. This outcome was an ordinal end point, with death as the worst outcome (labeled as −1) followed by the length of time alive and free of hospitalization, such that the best outcome would be 28 hospital-free days. If a patient had intervening days free of hospitalization and was then rehospitalized, the patient was given credit for the intervening days as free of hospitalization. We used a different primary outcome for the comparative effectiveness trial vs the cohort study because we hypothesized that, in addition to potential differences in 28-day hospitalization and mortality rates between mAb types (sotrovimab, casirivimab-imdevimab, and casirivimab-imdevimab or sotrovimab), there may be differences in hospital length of stay. The ordinal primary outcome for the trial allowed a single summary measure to encompass these potential differences.

The secondary outcome for the trial was mortality at 28 days. We evaluated outcomes stratified by infusion location (ED vs infusion center) and the frequency of adverse events. We assessed the prevalence of SARS-CoV-2 variants in a random subset of enrolled patients and in the Pennsylvania catchment area using GISAID (Global Initiative on Sharing All Influenza Data)⁷ (eFigure 1 in Supplement 2).