SEROLOGICAL RESPONSE FOLLOWING THREE DOSES of SARS-COV-2 MRNA VACCINE in PATIENTS with GIANT CELL ARTERITIS: EXPERIENCE of A SINGLE-CENTRE COHORT

ABSTRACT

Background: The spread of COVID-19 pandemic raised the need to perform an additional vaccine dose to overcome the diffusion of the infection and possible life-threatening disease complications. Certain population subsets seem to be at increased risk of developing such complications, such as elderly and/or immu-nocompromised patients. Objectives: To assess the persistence of immunity following SARS-CoV-2 mRNA vaccine and the magnitude of the humoral response after the booster dose in a cohort of patients affected by giant cell arteritis (GCA). Methods: Patients with GCA regularly followed at the Rheumatology Department of the University of Pavia, Italy, who received a booster dose of SARS-CoV-2 mRNA vaccine (BNT162b2 Pfizer/BioNtech or mRNA-1273 Moderna) between October 1st and December 31st, 2021 were included. Humoral response was assessed by measuring SARS-CoV-2 Trimeric S (TSAbs) and Neutralizing (NAbs) antibodies, with a cut-off of 33.8 Binding Antibody Units (BAU)/mL and 110 dilution, respectively. Blood samples from each patient were drawn at least 4 months after the second and three weeks after the third vaccine dose. Results: Forty-two patients who received the booster dose of SARS-CoV-2 mRNA vaccine were enrolled. Thirty (71.4%) were females, mean age 73.2±4.7 years, disease duration 58±38 months, 19 (45.2%) had large-vessel vasculitis. Thirty-two (76.2%) were on glucocorticoids (GCs) at a mean dose of 4.9±7.8 mg/day prednisone equivalent, with 7 (16.7%) receiving ≥7.5 mg/day. Eighteen (42.9%) were on methotrexate (MTX) (mean dose 14.2±3.5 mg/week) and 8 (19.0%) were treated with subcutaneous tocilizumab (TCZ) 162 mg/week. SARS-CoV-2 serology was tested prior to the third vaccine dose at an average of 5.4±0.4 months from the former vaccination scheduled 37 (88.1%) retained TSAbs and 30 (71.4%) NAbs. The median TSAb titre was 134 BAU/mL (IQR 97-292). Four out of 5 patients (80.0%) without TSAbs and 7 out of 12 (58.3%) without NAbs were on both GCs and MTX. Moreover, those on GCs plus MTX had lower pre-third dose TSAb titres as compared to other treatment subgroups (Figure 1A). GC doses ≥7.5 mg/day prednisone equivalents seemed to blunt NAb levels along time 28.6% patients on GCs ≥7.5 mg/day prednisone equivalents had negative NAbs before the third dose vs. 80.0% of those taking <7.5 mg/day (p=0.007) as well as lower NAb titres (Figure 1B). Data regarding antibody response after the booster dose were available for 35 patients (83.3%). Blood collection occurred at a median of 25 days (IQR 24-32) after the third vaccine dose. All patients developed TSAbs, even those who did not respond to the previous shots. The median TSAb titre rose to 2080 BAU/mL (IQR 2080-2080) (p<0.001), while the median NAb titre increased from 110 to 1320 (p<0.001). One patient (2.9%) treated with prednisone 8.75 mg/day plus MTX 12.5 mg/week did not develop NAbs. NAb levels were lower in patients taking MTX as compared to those who did not (Figure 1C,D), whereas treatment with TCZ or GCs, along with the GC dose, did not affect the magnitude of the antibody response. There were no serious adverse events from the vaccine. However, 3 patients (8.6%) experienced a disease relapse 24±5 days after the booster dose. Conclusion: In our cohort, most patients who seroconverted after the second dose of vaccine retained the humoral immunity, with excellent serocon-version rates following the booster dose. However, GCs, especially at doses ≥7.5 mg/day prednisone equivalents, may contribute to the waning of NAb titres. On the other hand, immunosuppressants like MTX, especially when combined with GCs, might impair the magnitude of the humoral response to the booster dose.