Antibody Response to the SARS-CoV-2 Vaccine and COVID-19 Vulnerability during the Omicron Pandemic in Patients with CLL: Two-Year Follow-Up of a Multicenter Study.

High morbidity and mortality due to COVID-19 were described in the pre-vaccination era in patients with chronic lymphocytic leukemia (CLL). To evaluate COVID-19 morbidity after the SARS-CoV-2 vaccine, we carried out a prospective study in 200 CLL patients. The median age of patients was 70 years; 35% showed IgG levels ≤ 550 mg/dL, 61% unmutated IGHV, and 34% showed TP53 disruption. Most patients, 83.5%, were previously treated, including 36% with ibrutinib and 37.5% with venetoclax. The serologic response rates to the second and third dose of the vaccine were 39% and 53%, respectively. With a median follow-up of 23.4 months, 41% of patients experienced COVID-19, 36.5% during the Omicron pandemic, and 10% had subsequent COVID-19 events. Severe COVID-19 requiring hospitalization was recorded in 26% of patients, and 4% died. Significant and independent factors associated with the response to the vaccine and vulnerability to COVID-19 were age (OR: 0.93; HR: 0.97) and less than 18 months between the start of targeted agents and vaccine (OR: 0.17; HR: 0.31). TP53 mutation and ≥two prior treatments also emerged as significant and independent factors associated with an increased risk of developing COVID-19 (HR: 1.85; HR: 2.08). No statistical difference in COVID-19 morbidity was found in patients with or without antibody response to the vaccine (47.5% vs. 52.5%; p = 0.21). Given the persistent risk of infection due to the continuous emergence of SARS-CoV-2 variants, our results support the importance of new vaccines and protective measures to prevent and mitigate COVID-19 in CLL patients.