In people with multiple sclerosis, anti-CD20 elicited suppression of humoral responses to COVID-19 vaccines is temporary. Production of antibodies was more prominent >18 months following termination of anti-CD20 therapy.

This retrospective observational study was held to examine the duration of the anti-CD20 therapy-induced impact on humoral responses to SARS-CoV-2 vaccines.

Multiple sclerosis patients who had discontinued anti-CD20 treatment for ⩾12 months and were devoid of immunomodulation were incorporated. Retrieval was done of demographics and lab parameters including B-cell counts and immunoglobulin (IgA, IgM, IgG) levels before anti-CD20 initiation (baseline) and longitudinally after anti-CD20 therapy cessation from the electronic medical records. A comparison was done between humoral responses to coronavirus vaccines and a population of 11 multiple sclerosis people with ongoing anti-CD20 medication (control cohort).

Overall, 24 multiple sclerosis patients discontinued anti-CD20 treatment for an average of 34 months. Antibody responses to coronavirus vaccines were available in 71% (17 people). Majority of people induced a quantifiable response of antibody to COVID-19 immunization on average 22 months from the last anti-CD20 infusion, which was higher in comparison with the population with ongoing anti-CD20 treatment.

Compared with the control cohort, remarkably elevated antibody levels were found among multiple sclerosis patients (vaccinated >18 months post-treatment discontinuation). Notably, 18 months post discontinuation of the therapy, mean B-cell counts approached normal ranges and the interindividual kinetics for the B-cell reconstitution were found to be heterogeneous. The humoral responses to the coronavirus vaccine were not correlated to B-cell recovery as no correlation between vaccine responses and B-cell repopulation was seen. Mean total IgA, IgM, and IgG levels continued to be in the reference range.

The immunological ‘scar’ of anti-CD20 therapy concerning vaccine responses and B-cell counts in multiple sclerosis patients seems to wane 18 months post-anti-CD20 cessation.