Abstract
Background: The impact of chronic therapeutic plasmapheresis on humoral response following COVID‐19 vaccination is poorly documented, especially among patients treated with double filtration plasmapheresis (DFPP). Objectives: This retrospective single‐center study evaluated the humoral response after SARS‐CoV‐2 vaccination and studied anti‐SPIKE seropositivity and antibody dynamics in patients with chronic DFPP at our institution. Method: All patients undergoing chronic DFPP at a tertiary center in France from December 2020 to November 2022 were included. We defined one patient subgroup as Group 1 to evaluate anti‐SPIKE seropositivity after vaccination, with three groups based on their anti‐SPIKE titers: (Group 1A) nonresponders (<0.8 UI/mL), (Group 1B) weak responders (0.8 to <250 binding antibody unit [BAU]/mL), and (Group 1C) strong responders (>250 BAU/mL). Group 2 served to evaluate antibody dynamics with anti‐SPIKE levels measured 3 months after initial vaccination, Group 2A having a sustained level and Group 2B a declining pattern. Results: The 21 patients included had a median age of 63 years, and 13 (56%) were male. The indications for chronic DFPP mainly included dysimmune pathologies (15; 71%) and familial dyslipidemia (6; 29%). For the humoral response to vaccination in Patient Group 1, the only nonresponder was a patient who had undergone kidney transplantation 30 months earlier and was on immunosuppressive medication. For Patient Group 2, the median follow‐up of antibody titers was 13 months [12–13]. Two distinct patterns of anti‐SPIKE dynamics were observed: a rapid decline in anti‐SPIKE antibody titers within 6 months following the initial vaccination or booster dose ( n = 10 [71.4%] Group 2A) and stable anti‐SPIKE levels above 250 BAU/mL over >6 months ( n = 4 [28.6%] Group 2B) with more patients with familial dyslipidemia in the former. Conclusions: Humoral response to SARS‐CoV‐2 vaccination appears robust in patients undergoing chronic DFPP and may be linked to patients' immune status rather than DFPTP itself. Our results support current recommendations for administering three doses of vaccine with a booster every 6 months.