Neutralizing Monoclonal Antibody Treatment Reduces Hospitalization for Mild and Moderate Coronavirus Disease 2019 (COVID-19): A Real-World Experience.

Background: Neutralizing monoclonal antibody (NmAb) treatments have received Emergency Use Authorization to treat patients with mild or moderate COVID-19 infection. To date, no real- world data on the efficacy of NmAbs have been reported from clinical practice. We assessed the impact of NmAb treatment given in the outpatient clinical practice setting on hospital utilization.

Methods: Electronic medical records were used to identify adult COVID-19 patients who received NmAbs (bamlanivimab [BAM] or casirivimab and imdevimab [REGN-COV2]) and historic COVID-19 controls. Post-index hospitalization rates were compared.

Results: 707 confirmed COVID-19 patients received NmAbs and 1709 historic COVID-19 controls were included; 553 (78%) received BAM, 154 (22%) received REGN-COV2. Patients receiving NmAb infusion had significantly lower hospitalization rates (5.8% vs 11.4%, P < .0001), shorter length of stay if hospitalized (mean, 5.2 vs 7.4 days; P = .02), and fewer ED visits within 30 days post-index (8.1% vs 12.3%, P = .003) than controls. Hospitalization-free survival was significantly longer in NmAb patients compared with controls (P < .0001). There was a trend towards a lower hospitalization rate among patients who received NmAbs within 2-4 days after symptom onset. In multivariate analysis, having received an NmAb transfusion was independently associated with a lower risk of hospitalization after adjustment for age, sex, race, BMI, and referral source (adjusted HR [95% CI], .54 [0.38-0.79]; P = .0012). Overall mortality was not different between the 2 groups.

Conclusions: NmAb treatment reduced hospital utilization, especially when received within a few days of symptom onset. Further study is needed to validate these findings.