Effectiveness of Severe Acute Respiratory Syndrome Coronavirus 2 Monoclonal Antibody Infusions in High-Risk Outpatients.

Background Coronavirus disease 2019 (COVID-19) continues to stress the health care system. Neutralizing monoclonal antibodies (mAbs) were effective in reducing COVID-19–related hospitalizations and emergency department (ED) visits in their respective clinical trials. However, these results have yet to be reproduced in a practical setting following implementation of current US Food and Drug Administration (FDA) guidance. Methods This retrospective cohort study included outpatients with confirmed COVID-19 infection, who had mild/moderate symptoms for 10 days or less, and who were deemed high-risk for severe COVID-19 under FDA's Emergency Use Authorization for mAbs. Patients who received either bamlanivimab or casirivimab/imdevimab from 18 November 2020 through 5 January 2021 were included (n = 200). This was compared against a control cohort of randomly selected high-risk COVID-19 outpatients who declined or were not referred for mAb treatment during the same period (n = 200). The primary outcome was a composite of 29-day COVID-19–related hospitalizations and/or ED visits. Prespecified secondary outcomes included the individual components of the primary endpoint, 29-day all-cause mortality, and serious adverse drug events. Results Patients treated with mAbs were significantly less likely to be hospitalized or visit the ED compared with patients not treated with mAb (13.5% vs 40.5%; odds ratio, 0.23 [95% confidence interval,.14–.38]; P  < .001). The mortality rate was 0% in the mAb group compared with 3.5% in the control group (P  = .02). Only 2 patients receiving mAb experienced a serious adverse event requiring treatment. Conclusions Among high-risk COVID-19 outpatients with mild/moderate symptoms, early administration of mAbs can potentially reduce the strain on the health care system during the current pandemic. [ABSTRACT FROM AUTHOR]