Third dose of SARS-CoV-2 vaccination in hemato-oncological patients and health care workers: immune responses and adverse events – a retrospective cohort study

•Anti-SARS-CoV-2 antibody levels diminished over time after the second vaccination.•Antibody levels increased after the third dose, supporting its administration.•Patients under B cell-targeting therapy showed considerably lower antibody levels.•Antibody levels correlated with CD19+ and CD56+ peripheral blood cell counts.•Lower antibody levels than in controls underline the need for further studies.