Antibody response to SARS-CoV-2 mRNA vaccines in patients with rheumatic diseases in Japan: Interim analysis of a multicenter cohort study

Background: To evaluate the impact of medication on antibody response to SARS-CoV-2 mRNA vaccines in Japanese patients with rheumatic diseases. Methods: This prospective multicenter cohort study evaluated the humoral response in 12 different medication groups. Antibody levels before the first vaccination and 3-6 weeks after the second vaccination were measured using the Elecsys Anti-SARS-CoV-2 S assay. Statistical analysis included comparing antibody titers among the different medication groups using the Kruskal–Wallis test followed by the Bonferroni–Dunn test for multiple comparisons and multiple linear regression analysis. Results: Three hundred and seventy-two patients receiving treatment for rheumatic diseases were enrolled, and 295 patients were analyzed. The seroconversion rate was 92.2% and the median antibody titer was 255 U/ml (interquartile range; IQR, 34.1-685) after the second mRNA vaccination. Antibody levels were significantly lower in the groups treated with TNF inhibitor (TNFi) with methotrexate (MTX) (median, 104 U/ml; IQR, 33.2-260), abatacept (median, 48.2 U/ml; IQR, 17.9-182), mycophenolate mofetil (MMF) (median, 3.24 U/ml; IQR, 0-34), MMF or mizoribine (MMF/MZR) combined with calcineurin inhibitor (CNI) (median, 5.5 U/ml; IQR, 0-21), and rituximab or cyclophosphamide (RTX/CPA) (median, 19.5 U/ml; IQR, 0-142) compared with those treated with sulfasalazine and/or bucillamine (median, 831 U/ml; IQR, 451-1451.5) or CNI (median, 833 U/ml; IQR, 164-1882) (p<0.01). Conclusions: Additional early vaccination is required in patients treated with TNFi and MTX, ABT, MMF, MMF or MZR combined with CNI and CPA/RTX. However, patients treated with CNI and sulfasalazine and/or bucillamine may be safer among patients with rheumatic diseases.