(653) Tixagevimab and Cilgavimab Reduced the Likelihood of Covid after Heart Transplant in the Age of Omicron

PURPOSE: SARS-CoV-2 infection (COVID) is associated with high morbidity and mortality in solid organ transplants and vaccine efficacy is suboptimal. Tixagevimab and cilgavimab (T/C) are neutralizing antibodies used in the U.S. under emergency use authorization for COVID pre-exposure prophylaxis. However, T/C were developed when the Alpha and Omega variants were dominant. The purpose of this study is to look at real-world efficacy of T/C during the Omicron phase of the pandemic in heart transplants (HT). METHODS: This was a retrospective study of adult HT recipients at a single center comparing those who received at least 3 doses of a COVID vaccine plus T/C versus those who only received the vaccine series (control) without prior infections. The primary outcome was development of COVID infection. Secondary outcomes included time from last vaccine to start of Omicron phase of pandemic, time from last vaccine to infection, and time from HT to infection. The Omicron phase was defined from 1/2022 to 2/2022. Chi-square and t-tests were used to assess for differences. RESULTS: Of the 244 patients identified, 44 received vaccination + T/C and 200 had vaccines only (Table 1). In the T/C group, patients were younger and more female (Table 1). In the control and T/C groups, 23% and 9.1% of patients, respectively, had documented COVID infections during the Omicron phase (p=0.039, Table 2). Months from last vaccine to start of Omicron phase, months from last vaccine to infection, and time from date of transplant to infection were similar between the two groups. Characteristics of the T/C patients who had breakthrough infections are shown in Table 3, none of whom required hospitalization or died. CONCLUSION: Patients who received vaccination + T/C had a significantly lower incidence of COVID infection compared to those who received vaccination alone in the Omicron era. T/C appeared to be protective in both recent and remote HT recipients, underscoring the utility of administering protective monoclonal antibodies in this population.