The humoral immune response developed after receiving the full vaccination schedule against
COVID-19 is impaired in individuals who received anti-CD20
therapy 6-9 months before vaccination. However, there is little information about the cellular immune responses elicited in these individuals. In this study, we analyzed the humoral and cellular immune responses in 18 individuals with
hematological disease who received the last dose of
rituximab 13.8 months (IQR 9.4-19) before the booster dose. One month after receiving the booster dose, the seroconversion rate in the
rituximab-treated cohort increased from 83.3% to 88.9% and titers of specific IgGs against SARS-CoV-2 increased 1.53-fold (p = 0.0098), while the levels of
neutralizing antibodies increased 3.03-fold (p = 0.0381). However, the cytotoxic activity of peripheral blood mononuclear cells (PBMCs) from
rituximab-treated individuals remained unchanged, and both antibody-dependent cellular cytotoxicity (ADCC) and direct cellular cytotoxicity (CDD) were reduced 1.7-fold (p = 0.0047) and 2.0-fold (p = 0.0086), respectively, in comparison with healthy donors.
Breakthrough infections rate was higher in our cohort of
rituximab-treated individuals (33.33%), although most of the infected patients (83.4%) developed a mild form of
COVID-19. In conclusion, our findings confirm a benefit in the humoral, but not in the cellular, immune response in
rituximab-treated individuals after receiving a booster dose of an
mRNA-based
vaccine against
COVID-19.