Is vaccine response to SARS-CoV-2 preserved after switching to anti-CD20 therapies in patients with multiple sclerosis or related disorders?

BACKGROUND: Although vaccination against SARS-CoV-2 is recommended prior to introducing anti-CD20 therapies, limited data are available regarding the evolution of post-vaccinal immunity. METHODS: This retrospective study compared anti-Spike antibody titres at 6 and 12 months from SARS-CoV-2 vaccination between patients vaccinated before switching to anti-CD20 ('Switch') and two control groups: (1) patients vaccinated under disease-modifying therapies (DMTs) other than fingolimod and anti-CD20 ('Other DMTs'); (2) patients vaccinated on anti-CD20 ('Anti-CD20'). Anti-Spike-specific T-cell responses were compared between 'Switch' and 'Anti-CD20' groups. RESULTS: Fifty-three patients were included in the 'Switch' group, 54 in the 'Other DMTs' group and 141 in the 'Anti-CD20' group. At 6 months, in the subset of patients who received a booster dose, the 'Switch' group had lower anti-Spike titres compared with the 'Other DMTs' group (median 241.0 IQR (88.0; 504.0) BAU/mL vs 2034 (1155; 4634) BAU/mL, p<0.001), and less patients in the 'Switch' group reached the protective threshold of 264 BAU/mL. The 'Switch' group had higher anti-Spike titres than the 'Anti-CD20' group (7.5 (0.0; 62.1) BAU/mL, p=0.001). Anti-Spike titres were not different between the 'Switch' and 'Other DMTs' groups before booster administration. These results were similar at 12 months. Spike-specific T-cell positivity was similar between the 'Switch' and 'Anti-CD20' groups at 6 and 12 months (60.4% vs 61.0%, p=0.53, and 79.4% vs 87.5%, p=0.31, respectively). CONCLUSIONS: Despite a primary vaccination performed before the first anti-CD20 cycle, our results suggest weaker immune responses at 6 and 12 months and decreased booster efficacy after introducing anti-CD20. Patients vaccinated prior to anti-CD20 introduction might falsely be considered as fully protected by vaccination.