Low levels of anti–SARS–CoV‐2 antibodies after vaccination in rituximab‐treated patients: comment on the article by Simon et al. Issue 5 (5th April 2022) - Evangelatos, Gerasimos; Kouna, Konstantina; Fragoulis, George E.; Moschopoulou, Melina; Triantafylli, Maria; Lekka, Antigoni; Iliopoulos, Alexios