Bivariate comparisons of serological responsiveness to the COVID-19 vaccine
| Factor | Overall | Negative for antibody response | Positive for antibody response | P value* |
| N (%) | N (%) | N (%) | ||
| N | 89 | 21 | 68 | |
| Age, mean (SD) | 61.3034 (16.081) | 65.4286 (15.0916) | 60.0294 (16.2692) | 0.18† |
| Sex | 0.38 | |||
| Female | 68 (76%) | 18 (86%) | 50 (74%) | |
| Male | 21 (24%) | 3 (14%) | 18 (26%) | |
| Race | 0.19 | |||
| White | 84 (94%) | 19 (90%) | 65 (96%) | |
| Black or African American | 2 (2%) | 0 (0%) | 2 (3%) | |
| Asian | 3 (3%) | 2 (10%) | 1 (1%) | |
| Primary diagnosis | ||||
| RA | 23 (26%) | 2 (10%) | 21 (31%) | 0.084 |
| Systemic lupus erythematosus | 9 (10%) | 2 (10%) | 7 (10%) | 1.00 |
| Sjogrens syndrome | 10 (11%) | 3 (14%) | 7 (10%) | 0.69 |
| Systemic sclerosis | 5 (6%) | 3 (14%) | 2 (3%) | 0.083 |
| Psoriatic arthritis | 6 (7%) | 0 (0%) | 6 (9%) | 0.33 |
| Granulomatosis with polyangiitis | 12 (13%) | 6 (29%) | 6 (9%) | 0.031 |
| Giant cell arteritis | 2 (2%) | 0 (0%) | 2 (3%) | 1.00 |
| Polymyalgia rheumatica | 3 (3%) | 1 (5%) | 2 (3%) | 0.56 |
| Microscopic polyangitis | 4 (4%) | 2 (10%) | 2 (3%) | 0.24 |
| IgG4 disease | 1 (1%) | 1 (5%) | 0 (0%) | 0.24 |
| Behcet’s disease | 2 (2%) | 0 (0%) | 2 (3%) | |
| Dermatomyositis | 1 (1%) | 0 (0%) | 1 (1.5%) | |
| Eosinophilic granulomatosis with polyangiitis (Churg-Strauss) | 1 (1%) | 0 (0%) | 1 (1.5%) | |
| Familial mediterranean fever | 1 (1%) | 0 (0%) | 1 (1.5%) | |
| Mixed connective tissue disease | 1 (1%) | 0 (0%) | 1 (1.5%) | |
| Osteoarthritis | 1 (1%) | 0 (0%) | 1 (1.5%) | |
| Relapsing polychondritis | 2 (2%) | 1 (5%) | 1 (1.5%) | |
| Retinal vasculitis | 2 (2%) | 0 (0%) | 2 (3%) | |
| Systemic lupus erythematosus/rheumatoid arthritis overlap syndrome | 1 (1%) | 0 (0%) | 1 (1.5%) | |
| Undifferentiated connective tissue disease | 2 (2%) | 0 (0%) | 2 (3%) | |
| Vaccine type | 1.00 | |||
| Pfizer | 51 (57%) | 12 (57%) | 39 (57%) | |
| Moderna | 38 (43%) | 9 (43%) | 29 (43%) | |
| COVID-19 antibody assay | ||||
| Roche elecsys anti-SARS-CoV-2 | 84 (94.38%) | – | – | |
| Siemens healthineers SARS-CoV-2 Total Assay Atellica IM or ADVIA Centaur XP/XPT‡ | 5 (5.62%) | – | – | |
| Days from last rituximab exposure to assay among Rituximab treated patients, median (IQR), (n=30) | 212 (122, 599) | 153 (114, 212) | 762 (599, 1064) | <0.001 |
| Days from last rituximab exposure to second dose of COVID-19 vaccine among rituximab-treated patients, median (IQR), (n=30) | 167 (79, 540) | 102 (66, 167) | 705 (540, 1035) | <0.001 |
| Time from last rituximab exposure to second dose of COVID-19 vaccine among Rituximab treated patients (n=30)§ | ||||
| <6 months | 16 (53%) | 16 (80%) | 0 (0%) | <0.001 |
| 6–12 months | 4 (13%) | 3 (15%) | 1 (10%) | |
| >12 months | 10 (33%) | 1 (5%) | 9 (90%) | |
| Prior documented COVID infection | 2 (2%) | – | – | |
| Medications ¶ | Number and percentage of overall group | Number and percentage of group negative for antibody response | Number and percentage of group positive for antibody response | |
| Patients with rituximab exposure in combination with other therapy | 15 (17%) | 10 (48%) | 5 (7%) | 1.00 |
| Patients without rituximab exposure treated with two or more medications | 20 (22%) | 1 (4%) | 19 (28%) | 0.34 |
| Patients on two or more medications | 35 (39%) | 11 (52%) | 24 (35%) | 0.20 |
| Non-Steroidal Anti-inflammatory Drugs | 6 (7%) | 0 (0%) | 6 (9%) | 0.33 |
| Corticosteroids | 17 (19%) | 5 (24%) | 12 (18%) | 0.54 |
| Non-biological DMARD ** | ||||
| Sulfasalazine | 1 (1%) | 0 (0%) | 1 (1%) | 1.00 |
| Leflunomide | 3 (3%) | 1 (5%) | 2 (3%) | 0.56 |
| Hydroxychloroquine | 19 (21%) | 2 (10%) | 17 (25%) | 0.22 |
| Azathioprine | 3 (3%) | 0 (0%) | 3 (4%) | 1.00 |
| Upadacitinib | 2 (2%) | 0 (0%) | 2 (3%) | 1.00 |
| Methotrexate | 13 (15%) | 1 (5%) | 12 (18%) | 0.29 |
| Apremilast | 1 (1%) | 0 (0%) | 1 (1%) | 1.00 |
| Mycophenolate mofetil | 7 (8%) | 3 (14%) | 4 (6%) | 0.35 |
| Tofacitinib | 4 (4%) | 0 (0%) | 4 (6%) | 0.57 |
| Colchicine | 3 (3%) | 0 (0%) | 3 (4%) | 1.00 |
| Biological DMARDs | ||||
| Adalimumab | 8 (9%) | 0 (0%) | 8 (12%) | 0.19 |
| Secukinumab | 2 (2%) | 0 (0%) | 2 (3%) | 1.00 |
| Mepolizumab | 1 (1%) | 0 (0%) | 1 (1%) | 1.00 |
| Tocilizumab | 2 (2%) | 1 (5%) | 1 (1%) | 0.42 |
| Etanercept | 1 (1%) | 0 (0%) | 1 (1%) | 1.00 |
| Abatacept | 1 (1%) | 0 (0%) | 1 (1%) | 1.00 |
| Belimumab | 2 (2%) | 1 (4.76%) | 1 (1.47%) | 0.42 |
| Rituximab | 30 (34%) | 20 (95%) | 10 (15%) | <0.001 |
| Antibody concentration (U/mL) in rituximab-treated patients (n=30), median (IQR) | – | 0 (0, 0) | 251 (169, 251) | <0.001†† |
*All p values were calculated from a Fisher’s exact test unless otherwise indicated.
†T-test was used.
‡Roche Elecsys Anti-SARS-CoV-2, specificity 99.8% sensitivity 99.5%, or a Siemens Healthineers SARS-CoV-2 total (COV2T) Assay Atellica IM, specificity 99.82% sensitivity 100% or ADVIA Centaur XP/XPT, specificity 99.81% sensitivity 100%.
§Among the four people who were negative, the specific number of days from last infusion to first vaccination were 188, 229, 230, 415.
¶Medications are not mutually exclusive. 35 (39%) patients are taking two or more medications.
**Includes both conventional and targeted synthetics.
††Wilcoxon rank sum test was used.
DMARDS, disease modifying antirheumatic drugs.