Objective:To investigate the vaccination status, characteristics and prognosis of patients suffering from a combination of COVID-19 and chronic lymphocytic anemia (CLL) in China.Methods:Clinical data of 328 patients with chronic lymphocytic leukemia (CLL) who were first diagnosed with COVID-19 and treated in the Department of Hematology of Jiangsu Provincial People’s Hospital between November 2022 and February 2023 were retrospectively analyzed. Univariate and multivariate analysis of data of patients with severe/critical COVID-19 were conducted by applying the binary logistic regression model.Results:The median age of the CLL patients was 60 (24-87) years. 23.5% (77/328) of these patients suffered from severe/critical COVID-19 infection. Univariate analysis of the data demonstrated that a combination of factors including age >67 years ( OR=2.15, 95% CI 1.24- 3.73, P=0.006), diabetes ( OR=2.09, 95% CI 1.05-4.20, P=0.037), chronic hepatitis B ( OR=2.91, 95% CI 1.30-6.51, P=0.010), CLL progressive ( OR=3.79, 95% CI 1.57-9.15, P=0.003) and CD20 antibody-based treatments within three months prior to the COVID-19 infection ( OR=2.79, 95% CI 1.35-5.77, P=0.006) were the risk factors for severe/critical COVID-19. According to the multivariate analysis, CLL progressive ( OR=2.98, 95% CI 1.10-8.10, P=0.033) was an independent risk factor for severe/critical COVID-19 and administration of the BTK (Bruton tyrosine kinase) inhibitor monotherapy might exert a protective effect and influence a positive outcome of the COVID-19 infection ( OR=0.38, 95% CI 0.16-0.90, P=0.028). Among the 242 patients who were followed up until October 2023, 9.1% (22/242) had multiple subsequent COVID-19 infections (≥3), and 2.1% (5/242) had persistent COVID-19 infections (patients with persistent positive test for the SARS-CoV-2 antigen testing until missing follow-up for any reason). The peak value of the anti-SARS-CoV-2-IgG titres was observed between three and four months post symptom onset (median: 3.511 S/CO vs 1.047 S/CO, P<0.05). The levels of immunoglobulin A gradually decreased following infection with COVID-19, and its trough levels were attained between two to four weeks post infection (median: 0.30 g/L vs 0.74 g/L, P<0.05). According to this study the mortality of patients suffering from a combination of COVID-19 infection and CLL was 2.7% (9/328), and the main reason for their death was respiratory failure and heart failure. Conclusions:A low rate of COVID-19 vaccination and a high rate of severe/critical COVID-19 infection was observed in the CLL patients. CLL progressive was associated with severe/critical COVID-19. Anti-CD20-based treatments received within the past three months might be a risk factor for exacerbation of COVID-19 infection, whereas a monotherapy with BTK inhibitors exert a protective effect and improve outcome of COVID-19 infection.