Monoclonal Antibodies for Averting Symptoms in SARS-CoV-2–Infected Seronegative Patients

The monoclonal antibody combination of casirivimab and imdevimab is effective when given intravenously for managing COVID-19 in outpatients at risk for severe disease (NEJM JW Infect Dis Nov 2021 and N Engl J Med 2021 Sep 29; [e-pub]). In Part A of a placebo-controlled, phase 3 study, investigators demonstrated the combination's efficacy at preventing infection when given subcutaneously to uninfected household contacts of patients with COVID-19 (NEJM JW Infect Dis Sep 2021 and N Engl J Med 2021 Aug 4; [e-pub]). Now, in Part B the investigators evaluated the combination's efficacy at preventing symptoms in household contacts who were found to be asymptomatically infected upon enrollment and who were seronegative. Among 207 such contacts (mea…