Real-World Effectiveness and Safety of Tixagevimab–Cilgavimab: A Target Trial Emulation Study

Abstract

Background: Immunocompromised individuals are at high risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and subsequent severe or fatal coronavirus disease 2019 (COVID-19), yet they have suboptimal responses to mRNA and inactivated COVID-19 vaccines. The efficacy of tixagevimab–cilgavimab in reducing symptomatic SARS-CoV-2 infection was demonstrated in phase III clinical trials. Nevertheless, real-world data on the effectiveness and safety of tixagevimab–cilgavimab remain limited. Objective: The aim was to evaluate the effectiveness and safety of tixagevimab–cilgavimab among immunocompromised individuals. Methods: Adults who were immunocompromised or receiving immunosuppressive therapies were included in this target trial emulation using territory-wide electronic health records in Hong Kong. A sequential trial emulation approach was adopted to compare effectiveness and safety outcomes between individuals who received tixagevimab–cilgavimab and individuals who did not. Results: A total of 746 tixagevimab–cilgavimab recipients and 2980 controls were included from 1 May 2022 to 30 November 2022. Tixagevimab–cilgavimab significantly reduced the risk of COVID-19 infection (hazard ratio [HR] 0.708, 95% confidence interval [CI] 0.527–0.951) during a median follow-up of 60 days. No significant difference was observed in the risk of COVID-19-related hospitalisation. Zero versus eight COVID-19 mortality cases and zero versus two severe COVID-19 cases were observed in tixagevimab–cilgavimab recipients and controls, respectively. Notably, significant risk reduction in COVID-19 infection was also observed among immunocompromised individuals who had been previously vaccinated with three or more doses of COVID-19 vaccine, or had no prior COVID-19 infection history. Conclusions: Tixagevimab–cilgavimab was effective in reducing COVID-19 infection among immunocompromised patients during the Omicron wave. Findings were consistent among individuals who previously received three or more doses of COVID-19 vaccine, or had no previous history of COVID-19 infection.