Background Patients with systemic lupus erythematosus (SLE) should be more proactive with the administration of the COVID-19 vaccine, as their systemic conditions are prone to developing severe outcomes. However, there are concerns that immunosuppressive agents used in SLE patients could reduce the immune response. Previous data demonstrates that total B-cell depletion impairs the humoral response in patients treated with Rituximab, but there is very limited information about Belimumab. Thus, we aimed to assess the immunogenicity and safety of COVID-19 vaccine in SLE patients treated with Belimumab.

Methods Patients with SLE receiving B-cell targeted therapy with Belimumab were recruited from December 14, 2021, to June 17, 2022. We reviewed the patients’ immunization history and measured the antibody titers of patients who had completed their third dose of COVID-19 vaccine. SARS-CoV-2 antibody titers were determined through semiquantitative anti-SARS-CoV-2 S enzyme immunoassay.

Results A total of 21 patients with SLE receiving Belimumab treatment were surveyed, out of which 10 patients had completed 3 doses of COVID-19 vaccinations. The mean duration between the last (3rd) vaccination date and the date of sample acquisition was 22.5 weeks, and there was no patient with side effects other than mild myalgia. The antibody titers were positive in all 10 patients, with 8 patients showing high antibody titers of 250 U/mL or more. The other 2 patients measured relatively low antibody titers of 117 U/mL and 112 U/mL, with a treatment history with Rituximab within one year and current treatment with hydroxychloroquine, respectively.

Conclusions Our findings suggest that Belimumab does not compromise the antibody production from the vaccination. SLE patients with Belimumab need not be reluctant to get COVID-19 vaccines in regard to humoral response impairment.