Can a Subcutaneous Shot of Monoclonal Antibodies Prevent COVID-19?

Postexposure prophylaxis with immunoglobulins has been the standard of care for many infectious diseases; thus, an effective immunoglobulin preparation for COVID-19 would provide a powerful new public health approach to controlling the current pandemic. Researchers conducted a manufacturer-supported placebo-controlled trial to assess the effectiveness of the REGEN-COV dual monoclonal antibody cocktail (casirivimab and imdevimab) given by subcutaneous injection as postexposure prophylaxis for symptomatic and asymptomatic COVID-19 in adolescent and adult household contacts of patients with the disease. Participants were randomized within 96 hours of COVID-19 diagnosis in the index patient. Analysis of these contacts was stratified by whether or not they themselves were SARS-CoV-2 infected; the current analysis is limited to the uninfected cohort.

Among 1505 household contacts with no evidence of current or prior SARS-CoV-2 infection, 30.5% were considered at high risk for severe COVID-19. Symptomatic COVID-19 cases occurred in 1.5% of REGEN-COV recipients versus 7.8% of placebo recipients (relative risk reduction, 81.4%). Findings were consistent for various definitions of symptomatic disease, for patients at high risk for progression, and for all age groups. Similar protection was achieved against asymptomatic infection. In addition, risk for having SARS-CoV-2 viral loads >10⁴ copies/mL was reduced, and the duration of having a high viral load was shortened. No significant adverse events were noted.