Table 2.
Immunogenicity of influenza vaccination, showing antibody titers, fold changes in antibody titers, vaccine response, and SP rates before and after vaccination according to individual strains in the vaccine*
| 1‐week MTX hold group (n = 90) | 2‐week MTX hold group (n = 88) | Healthy control group† (n = 62) | P ‡ | |
|---|---|---|---|---|
| H1N1 | ||||
| Prevaccination titer, GMT (95% CI) | 16.8 (13.9–20.2) | 15.9 (12.9–19.7) | 15.6 (12–20.5) | 0.592 |
| Postvaccination titer, GMT (95% CI) | 165 (129.1–210.9) | 185.8 (146.6–235.6) | 154.7 (117.5–203.7) | 0.389 |
| Fold increase, GMT (95% CI) | 9.8 (7.6–12.7) | 11.7 (8.8–15.5) | 9.9 (7.1–13.7) | 0.247 |
| Satisfactory vaccine response | 78 (86.7) | 73 (83.0) | 51 (82.3) | 0.490 |
| Prevaccination SP | 28 (31.1) | 25 (28.4) | 17 (27.4) | 0.693 |
| Postvaccination SP | 83 (92.2) | 84 (95.5) | 58 (93.5) | 0.371 |
| H3N2 | ||||
| Prevaccination titer, GMT (95% CI) | 29 (23.8–35.2) | 24.4 (20.1–29.5) | 23.4 (18.2–30.2) | 0.276 |
| Postvaccination titer, GMT (95% CI) | 138.2 (109.3–174.8) | 128.3 (102.2–161.1) | 75.7 (57.9–98.8) | 0.396 |
| Fold increase, GMT (95% CI) | 4.8 (3.7–6.2) | 5.3 (4–6.9) | 3.2 (2.4–4.4) | 0.712 |
| Satisfactory vaccine response | 53 (58.9) | 56 (63.6) | 31 (50.0) | 0.452 |
| Prevaccination SP | 47 (52.2) | 41 (46.6) | 28 (45.2) | 0.452 |
| Postvaccination SP | 83 (92.2) | 85 (96.6) | 53 (85.5) | 0.330 |
| B/Yamagata lineage | ||||
| Prevaccination titer, GMT (95% CI) | 34 (28.2–41.1) | 24.6 (19.4–31.1) | 12 (9.5–15.1) | 0.025 |
| Postvaccination titer, GMT (95% CI) | 86.4 (71.5–104.4) | 76.3 (60.7–96) | 33.8 (26.4–43.3) | 0.526 |
| Fold increase, GMT (95% CI) | 2.5 (2.1–3.1) | 3.1 (2.5–3.9) | 2.8 (2.2–3.6) | 0.132 |
| Satisfactory vaccine response | 32 (35.6) | 38 (43.2) | 28 (45.2) | 0.298 |
| Prevaccination SP | 53 (58.9) | 41 (46.6) | 27 (43.5) | 0.100 |
| Postvaccination SP | 84 (93.3) | 74 (84.1) | 50 (80.6) | 0.051 |
| B/Victoria lineage | ||||
| Prevaccination titer, GMT (95% CI) | 17.1 (14.4–20.4) | 16.4 (13.7–19.7) | 27.1 (20.6–35.5) | 0.537 |
| Postvaccination titer, GMT (95% CI) | 61.6 (49.7–76.3) | 57.5 (45.8–72) | 69.2 (53.5–89.5) | 0.888 |
| Fold increase, GMT (95% CI) | 3.6 (2.9–4.5) | 3.5 (2.7–4.5) | 2.6 (2–3.2) | 0.680 |
| Satisfactory vaccine response | 47 (52.2) | 41 (46.6) | 26 (41.9) | 0.452 |
| Prevaccination SP | 27 (30.0) | 21 (23.9) | 14 (22.6) | 0.356 |
| Postvaccination SP | 71 (78.9) | 68 (77.3) | 40 (64.5) | 0.794 |
Except where indicated otherwise, values are the number (%) of people/group. Antibody titers and fold increase in titers before and after vaccination are expressed as the geometric mean titer (GMT). A satisfactory vaccine response (i.e., seroconversion) was defined as a ≥4‐fold improvement in titers relative to baseline. Seroprotection (SP) was defined as titers of ≥1:40. 95% CI = 95% confidence interval.
The control group served as a reference group. The study was not powered to test the equivalence or superiority of the methotrexate (MTX) hold group versus controls.
Comparison between the 1‐week MTX and the 2‐week MTX hold groups. P values were generated by independent t‐tests for continuous variables and chi‐square tests for categorical variables.