Tixagevimab/cilgavimab pre-exposure prophylaxis is associated with lower breakthrough infection risk in vaccinated solid organ transplant recipients during the omicron wave

| 3135 AJT AL JURDI et AL. We also found that tixagevimab/cilgavimab use was associated with a lower incidence of breakthrough infection regardless of whether SOTRs had received 0-3 or 4-5 vaccines doses. Separate analysis of SOTRs who received 0-2 or 5 vaccine doses was not performed due to the small number of SOTRs in these groups. In addition, we found that tixagevimab/cilgavimab use was associated with a lower risk of breakthrough infection in kidney and lung transplant recipients. There was no statistically significant difference in the risk of breakthrough infection between liver or liver/kidney transplant recipients who did and did not receive tixagevimab/cilgavimab. However, given the small number of liver and liver/kidney transplant recipients in our cohort, our study was underpowered to find differences in this subgroup of SOTRs. Importantly, we also found a higher incidence of breakthrough infections in the low-dose (150-150 mg) compared to the high-dose (300-300 mg) tixagevimab/cilgavimab cohort, suggesting a lower risk of breakthrough infections in the high-dose group, which supports the FDA's revised recommendation to use the higher dose for preexposure prophylaxis in SOTRs. 14 A randomized controlled trial comparing the two doses would provide further evidence supporting the difference in breakthrough infection between the two doses in SOTRs. We also found that tixagevimab/cilgavimab was safe with a low rate of adverse events and no evidence of allograft..