Table 1 Participant characteristics
|  | Total (N = 2377) | RA (n = 1563, 65.8%) | PsA (n = 415, 17.5%) | SpA (n = 399, 16.8%) |
|---|---|---|---|---|
Age, years, median (IQR) | 62.0 (52.0–71.0) | 65.0 (58.0–73.0) | 59.0 (49.0–68.0) | 48.0 (38.0–60.0) |
Males, n (%) | 820 (34.5) | 323 (20.7) | 200 (48.2) | 297 (74.4) |
Race | Â | Â | Â | Â |
 Chinese, n (%) | 1701 (71.6) | 1112 (71.1) | 268 (64.6) | 321 (80.5) |
 Malay, n (%) | 238 (10.0) | 168 (10.7) | 48 (11.6) | 22 (5.5) |
 Indian, n (%) | 298 (12.5) | 186 (11.9) | 75 (18.1) | 37 (9.3) |
 Others, n (%) | 140 (5.9) | 97 (6.2) | 24 (5.8) | 19 (4.8) |
Disease activity before vaccination | ||||
 Remission, n (%) | 1093 (46.0) | 764 (48.9) | 169 (40.7) | 160 (40.1) |
 Low disease activity, n (%) | 953 (40.1) | 632 (40.4) | 169 (40.7) | 152 (38.1) |
 Moderate disease activity, n (%) | 290 (12.2) | 145 (9.3) | 72 (17.3) | 73 (18.3) |
 High disease activity, n (%) | 41 (1.7) | 22 (1.4) | 5 (1.2) | 14 (3.5) |
COVID-19 vaccine type | ||||
 Pfizer, n (%) | 2082 (87.6) | 1387 (88.7) | 357 (86.0) | 338 (84.7) |
 Moderna, n (%) | 295 (12.4) | 176 (11.3) | 58 (14.0) | 61 (15.3) |
Received two vaccine doses, n (%) | 2216 (93.2) | 1468 (93.9) | 381 (91.8) | 367 (92.0) |
Time from first to second Pfizer dose, days, median (IQR) | 21.0 (21.0–22.0) | 21.0 (21.0–22.0) | 21.0 (21.0–23.0) | 21.0 (21.0–24.0) |
Time from first to second Moderna dose, days, median (IQR) | 28.0 (28.0–32.0) | 28.0 (28.0–30.0) | 28.0 (28.0–32.0) | 29.0 (28.0–35.0) |
Treatment with conventional synthetic DMARDs | ||||
 Methotrexate, n (%) | 1186 (49.9) | 921 (58.9) | 228 (54.9) | 37 (9.3) |
 Leflunomide, n (%) | 217 (9.1) | 179 (11.5) | 27 (6.5) | 11 (2.8) |
 Sulfasalazine, n (%) | 626 (26.3) | 426 (27.3) | 102 (24.6) | 98 (24.6) |
 Antimalarials (chloroquine/hydroxychloroquine), n (%) | 436 (18.3) | 423 (27.1) | 8 (1.9) | 5 (1.3) |
Treatment with biological DMARDs | ||||
 IL6 inhibitors, n (%) | 10 (0.4) | 10 (0.6) | 0 (0) | 0 (0) |
 IL12/23 inhibitors, n (%) | 1 (< 0.1) | 0 (0) | 1 (0.2) | 0 (0) |
 IL23 inhibitors, n (%) | 2 (0.1) | 0 (0) | 2 (0.5) | 0 (0) |
 IL17 inhibitors, n (%) | 32 (1.3) | 0 (0) | 15 (3.6) | 17 (4.3) |
 TNF inhibitors, n (%) | 212 (8.9) | 57 (3.6) | 78 (18.8) | 77 (19.3) |
 Rituximab, n (%) | 5 (0.2) | 5 (0.3) | 0 (0) | 0 (0) |
Treatment with JAK inhibitors, n (%) | 33 (1.4) | 28 (1.8) | 2 (0.5) | 3 (0.8) |
Treatment with immunosuppressants | ||||
 Azathioprine, n (%) | 10 (0.4) | 7 (0.4) | 0 (0) | 3 (0.8) |
 Cyclophosphamide, n (%) | 3 (0.1) | 2 (0.1) | 1 (0.2) | 0 (0) |
 Cyclosporine, n (%) | 26 (1.1) | 10 (0.6) | 15 (3.6) | 1 (0.3) |
 Mycophenolate mofetil/mycophenolic acid, n (%) | 7 (0.3) | 7 (0.4) | 0 (0) | 0 (0) |
 Tacrolimus, n (%) | 1 (< 0.1) | 1 (0.1) | 0 (0) | 0 (0) |
Treatment with glucocorticoids, n (%) | 844 (35.5) | 749 (47.9) | 65 (15.7) | 30 (7.5) |
Treatment interruption, n (%) | 14 (0.6) | 8 (0.5) | 4 (1.0) | 2 (0.5) |