Ryan Wilson1, Junaid Awan2, Mary Brady2, Ciara Hunt2, Fahd Adeeb3 and alexander fraser4, 1University of Limerick, Buncrana, Ireland, 2University of Limerick, Limerick, Ireland, 3RCSI & UCD (Ireland) Malaysia Campus (RUMC), Malaysia, Malaysia, 4HSE, Limerick, Ireland
Background/Purpose: COVID-19 has increased the mortality rates among rheumatic patients, mainly those immunocompromised or with underlying comorbidities. During the COVID-19 vaccine development, patients on immunomodulatory drugs such as rituximab (RTX) were excluded from the trials due to their "high risk" categorization.
Aim: Assess the seroconversion rate of RTX-treated rheumatic patients on the COVID-19 vaccine.
Methods: An observational cohort study on adult patients with various established inflammatory rheumatic diseases at UL Hospitals Group, Limerick receiving ≥2 COVID-19 vaccination and on scheduled RTX infusion (received ≥1 dose). Patients were stratified based on time post-immunization (< 1 month, 1-3 months, 3-6 months, and >6 months post-vaccination). Samples (taken ≥14 days after the latest vaccination) were analyzed using the Elecsys anti-SARS-CoV-2 immunoassay for in vitro qualitative detection of IgG antibodies to SARS-COV-2, and screened for quantitative detection of anti-SARS-COV-2 nucleocapsid antigen (for previous COVID-19 infection) and anti-SARS-COV-2 spike protein (for immune response to the vaccine). The control group included patients on anti-TNF and tocilizumab (TOC). Seroconversion in response to the SARs-COV-2 is determined at >0.80 U/mL based on the manufacturer's guidelines.
Results: 49 patients were included (38 on RTX, 8 anti-TNFs, 3 TOC). Seroconversion rates were higher in the 1-3-month (75%) and 3-6-month (77%) RTX timelines; however, rates at 1 and 6 months were equal (60%) indicating antibody waning over this time period may not be significant in affecting seroconversion rates (levels remained ≥0.80 U/mL threshold). Whilst average seroconversion for the entire RTX cohort is 68.4%, the highest rates were seen in patients with a 6-month gap (90.9%). The lowest rates were seen in patients receiving immunization in the 2 week-3 months following RTX (57.14%), while the 3-6 months group showed slight improvement (62.5%). The patient population receiving anti-TNFs and TOC showed a 100% seroconversion rate.
Conclusion: Our data shows that a third of RTX patients treated didn't achieve seroconversion following immunization against SARS-COV-2 while the highest rates were seen in patients who had a 6-month gap. This data suggests benefit for delaying RTX infusion greater than the standard 6-month interval in suitable patients, prior to vaccination, to allow patients to reach adequate seroconversion against COVID-19 before reinitiating treatment.
Analysis of rates of seroconversion in rituximab patients from the time of infusion to vaccination.
Analysis of median antibody levels in rituximab patients from the time of infusion to vaccination.
R. Wilson: None; J. Awan: None; M. Brady: None; C. Hunt: None; F. Adeeb: None; a. fraser: None.