Casivirimab/Imdevimab Effect on COVID-19 Outcome and Reinfection in a Real-World SARS-COV-2 Variant Transition Period Setting.

Monoclonal antibodies targeted against SARS-COV-2 have been recruited in the challenging treatment of COVID-19 with few clinically significant side effects. Casivirimab/imdevimab, a combination of monoclonal antibodies targeted against SARS-COV-2 spike protein, was shown to effectively prevent recently infected high-risk COVID-19 patients from developing severe disease. Its efficacy waned with the emergence of the resistant omicron variant in late 2021. We recorded the real-world effect of casivirimab/imdevimab on 116 high-risk COVID-19 patients. Cumulative need for hospitalization, mortality, new-onset disease, and reinfections was monitored. Casivirimab/imdevimab effect was independent from previous immunization. The cohort was further divided into two subgroups: patients infected during a delta variant prevalent period were more likely to become admitted but as likely to die than patients infected with the omicron variant, in support of its protective effect from clinical studies. Cumulative reinfection incidence in treated patients, interestingly, was lower than in the general population.