[Prophylactic efficacy of tixagevimab/cilgavimab in patients with hematological neoplasms: a single-center study].

We retrospectively analyzed the efficacy of tixagevimab/cilgavimab (Tix/Cil) in 142 patients (total of 157 injections) with hematological disorders. Fifteen patients (9.5%) were infected with coronavirus disease (COVID-19), and 3 of these remained infected even after repeated administration of Tix/Cil. Malignant lymphoma and multiple myeloma were the most frequent underlying disorders (frequencies of 18.9% and 17.5%, respectively). Whole genome sequencing of the Omicron variant was performed in 11 patients, and revealed sensitivity to Tix/Cil in only 2. In both cases, the severity of COVID-19 was moderate I or II. Since April 2023, when a Tix/Cil-resistant variant became dominant (frequency >70%), the incidence of breakthrough infections increased from 4% to 35%, and none responded to Tix/Cil. Vaccination, together with daily precautions against infection, is the current approach used to prevent COVID-19, particularly in patients with lymphoid malignancies, because Tix/Cil is no longer effective as prophylaxis.