Doubtful clinical benefit of casirivimab-imdevimab treatment for disease severity outcome of high-risk patients with SARS-CoV-2 delta variant infection

Casirivimab/Imdevimab therapy reportedly retains neutralization potency against circulating SARS-CoV-2 variants, including Delta (B.1.617.2), but there are sparse data on its clinical benefit against the Delta variant among vaccinated and unvaccinated patients. We explored its therapeutic effect on COVID-19 severity outcome in terms of room air saturation <93% within 14 days of initial presentation and 45 day all cause mortality among high-risk patients with SARS-CoV-2 Delta variant infection and compared its effect between vaccinated and unvaccinated patients. We conducted a retrospective cohort study at a tertiary care medical center between 6/2021 and 9/2021 and included patients who presented with a positive PCR for SARS-CoV-2 and fulfilled the criteria for Casirivimab/Imdevimab treatment. Of the 359 suitable patients (52% female, median age 63 years), 116 were treated with Casirivimab/Imdevimab and 243 were not. Two hundred and one (56%) patients had received at least 2 SARS-CoV-2 vaccinations. Casirivimab/Imdevimab treatment was not an independent protective factor of COVID 19 severity outcome (multivariable analysis). Chronic kidney disease (aOR=3.51 [95%CI: 1.34 to 9.20], P=0.01), lower saturation levels (aOR=0.7 [95%CI: 0.58 to 0.85], P<0.01), abnormal chest x ray findings (aOR=2.92, [95%CI: 1.24 to 6.87, P=0.01), and higher C-reactive protein levels (aOR=1.01 [95%CI: 1.00 to 1.01], P=0.008) were independent risk factors of COVID-19 severity. Positive immunization status was an independent protective factor (aOR=0.33 [95%CI: 0.14 to 0.77], P=0.01). A sub analysis of patients treated with Casirivimab/Imdevimab revealed no significant difference in COVID-19 severity between vaccinated and unvaccinated patients. These findings demonstrate no added benefit of Casrivimab/Imdevinab treatment for high-risk patients with the SARS-CoV-2 Delta variant infection, regardless of their vaccination status.