ABSTRACT
BACKGROUND Real-world data on the effectiveness of neutralizing Casirivimab-Imdevimab monoclonal antibody (Cas-Imd mAb) against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection among high-risk patients may inform the response to future SARS-CoV-2 variants. METHODS This study covers an observational retrospective data analysis in Banner Health Care System sites, mainly in Arizona. During the study period, the prevalence of SARS-CoV-2 Delta variant was between 95% and 100%. Out of 29,635 patients who tested positive for COVID-19 between 8/1/2021 and 10/30/2021, in Banner Health Care System, the study cohort was split into 4213 adult patients who received Cas-Imd mAb (1200 mg) treatment compared to a propensity-matched 4213 untreated patients. The primary outcomes were the incidence of all-cause hospitalization, intensive care unit (ICU) admission, and mortality within 30 days of Cas-Imd mAb administration or COVID-19 Delta variant infection. RESULTS Compared to the propensity matched untreated cohort, the Cas-Imd mAb cohort had significantly lower all-cause hospitalization (4.2% vs 17.6%;difference in percentages and 95% confidence interval [CI] -13.4 [-14,7, -12.0], P <.001), ICU admission (0.3% vs 2.8%;difference and CI -2.4 [-3.0, -1.9], P <.001), and mortality (0.2% vs 2.0%;difference and CI -1.8 [-2.3, -1.3], P <.001) within 30 days. The Cas-Imd mAb treatment was associated with lower rate of hospitalization (hazard ratio [HR], 0.22;95% CI, 0.19-0.26; P <.001) and mortality (HR, 0.11;95% CI, 0.06-0.21; P<.001). CONCLUSIONS Cas-Imd mAb treatment was associated with a lower hospitalization rate, ICU admission, and mortality within 30 days among patients infected with COVID-19 Delta variant.