Two treatments that block vaccine responses are fingolimod and anti CD20 antibodies. They also block circulating antibodies and this can be a biomarker for infection. Here they say antibody IgG don’t drop after a switch from fingo to ocrelizumab or rituximab. However they look upt a year and IgG drops after antiCD20 are slow and looking at IgM may be a better indicator. Low levels of antibody after anti CD20 has suggested to be different de0endjnv on the antibody
Perriguey M, Rigollet C, Freeman SA, Graille-Avy L, Lafontaine JC, Lemarchant B, Alberto T, Demortière S, Boutiere C, Rico A, Hilézian F, Durozard P, Pelletier J, Maarouf A, Zéphir H, Audoin B. Prevalence of hypogammaglobulinemia after non-anti-CD20 therapies and impact of switching to rituximab/ocrelizumab in multiple sclerosis. Neurotherapeutics. 2025 Oct 4:e00760. doi: 10.1016/j.neurot.2025.e00760. Epub ahead of print. PMID: 41047296.
Source: multiple-sclerosis-research.org