Seroconversion after a third COVID-19 vaccine is affected by rituximab dose but persistence is not in patients with rheumatoid arthritis.

ABSTRACT

OBJECTIVES: In patients with rheumatoid arthritis (RA) treated with (ultra-)low dose rituximab (RTX), we investigated (1) the association of dosing and timing of rituximab (RTX) on seroconversion after third COVID-19 vaccination, and (2) persistence of humoral response after two-dose vaccination. METHODS: In this monocentre observational study, patients from the COVAC-cohort were included in the third vaccine analysis if humoral response was obtained 2-6 weeks after third vaccination in previous non-responders, and in the persistence analysis if a follow-up humoral response was obtained before third vaccination in previous responders. Dichotomization between 'positive' and 'negative' response was based on the assay cut-off. The association between latest RTX dose before first vaccination, timing between latest rituximab and vaccination, and response was analysed with univariable logistic regression. RESULTS: Of the 196 patients in the cohort, 98 were included in the third vaccine analysis and 23 in the persistence analysis. Third vaccination response was 19/98 (19%) and higher for 200 mg RTX users (5/13, 38%) than 500 and 1000 mg (7/37, 19% and 7/48, 15%). Non-significant trends were seen for higher response with lower dosing (200 versus 1000 mg OR 3.66, 95% CI 0.93-14.0) and later timing (per month since infusion OR 1.16, 0.97-1.35). Humoral response persisted in 96% (22/23) and in 89% (8/9) of patients who received RTX between the two measurements. CONCLUSION: Repeated vaccination as late as possible after the lowest RTX dose possible seems the best vaccination strategy. A once positive humoral response after COVID-19 vaccination persists irrespective of intercurrent rituximab infusion. TRIAL REGISTRATION Netherlands Trial Register, https//www.trialregister.nl/, NL9342.