The neutralizing monoclonal antibody combination of tixagevimab/cilgavimab has been shown to reduce the risk of SARS-CoV-2 infection in unvaccinated individuals during the Alpha (B.1.1.7) and Delta (B.1.617.2) waves. However, data on efficacy and safety of tixagevimab/cilgavimab in vaccinated solid organ transplant recipients during the Omicron wave is limited. To address this, we conducted a retrospective cohort study comparing 222 solid organ transplant recipients who received tixagevimab/cilgavimab for pre-exposure prophylaxis and 222 age-matched vaccinated solid organ transplant recipients who did not receive tixagevimab/cilgavimab. Subjects were followed for a mean of 67 (standard deviation 18) days. Kaplan-Meier estimates of the 60-day incidence of breakthrough infection were 1.8% in the tixagevimab/cilgavimab group and 4.7% in the control group (P = 0.045). Adverse events were uncommon, occurring in 4% of our cohort and most were mild. There was no significant change in serum creatinine or liver chemistries in kidney and liver transplant recipients respectively. In conclusion, we found that tixagevimab/cilgavimab use is safe and associated with a lower risk of breakthrough SARS-CoV-2 infection in vaccinated solid organ transplant recipients during the Omicron wave.

The authors have declared no competing interest.

The study was supported in part by the Harold and Ellen Danser Endowed/Distinguished Chair in Transplantation at Massachusetts General Hospital (Boston, MA, USA).

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The study was approved by the Mass General Brigham institutional review board (protocol numbers: 2021P001235, 2019P002526 and 2017P000336).

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Data to support the findings in the study are available from the corresponding author upon request.