When Chinese patients with plasma cell disorders encountered the nationwide Omicron outbreak (December 2022): a real-world multicenter and multiregional study.

Objectives: This study aims to assess the impact of the nationwide Omicron outbreak in December 2022 on Chinese patients with plasma cell disorders (PCD), focusing on the clinical characteristics of PCD patients with COVID-19 and the risk factors contributing to adverse clinical courses (severity and hospitalization) and outcomes.

Methods: A multicenter retrospective study was performed from December 1, 2022, to January 19, 2023. The study population includes 404 PCD patients, divided into a COVID-19 group (n = 342) and an uninfected group (n = 62).

Results: The frequency of COVID-19 infection was 84.7% (342/404), and 16.4% (56/342) were severe COVID-19. Among the 277 patients with complete follow-up, 2 deaths (0.7%) were reported, while 231 (83.4%) recovered from COVID-19. Age > 65 (P = 0.02) and prior anti-CD38 monoclonal antibody (mAb) treatment within six months (P = 0.03) were independent risk factors for severe infection. Additionally, previous chimeric antigen receptor T-cell (CAR-T) therapy within six months was correlated with a higher risk of hospitalization (P = 0.04) and prolonged recovery time (P = 0.03). No significant protective effect of vaccination on infection or severe infection was observed (P > 0.05).

Conclusions: The latest Omicron outbreak results in higher rates of severe infection and mortality in PCD patients compared with the general population in China, highlighting the need to protect this vulnerable population during the pandemic. Recent use of anti-CD38 mAb and CAR-T therapy are associated with poorer clinical courses and outcomes of PCD patients with COVID-19.