Humoral response to coronavirus disease-19 vaccines is dependent on dosage and timing of rituximab in patients with rheumatoid arthritis

OBJECTIVES: Humoral response to vaccines in RA patients treated with rituximab (RTX) in standard dosages (≥1000 mg) is decreased. Ultra-low dosages (500 or 200 mg) may have better response. Also, timing after latest RTX infusion may be an important variable. We aimed to investigate the influence of RTX dosage and timing on response to COVID-19 vaccination in RA patients. METHODS: A single-centre observational study (n = 196) investigated the humoral response, measured by total Ig anti-COVID-19 assay (positive response ≥1.1), 2-6 weeks after complete COVID-19 vaccination. A multivariable logistic regression model was built to study the effect of RTX dosage and time between latest rituximab and vaccination on response, adjusting for age and methotrexate use. RESULTS: After two-dose vaccination, the response rate was significantly better for patients receiving 200 mg (n = 31, 45%) rituximab compared with 1000 mg (n = 98, 26%; odds ratio 3.07, 95% CI 1.14-8.27) and for each additional month between latest rituximab and vaccination (OR 1.67, 1.39-2.01). CONCLUSION: Both increased time between latest rituximab infusion and complete vaccination, and 200 mg as latest dose were associated with a better response to COVID-19 vaccination and should be considered when trying to increase vaccine response after rituximab in RA patients. TRIAL REGISTRATION: Netherlands Trial Register, https://www.trialregister.nl/, NL9342.