Table 2. Risk of ischemic stroke in unvaccinated and vaccinated patients.
| All Group (n = 6570) | Unvaccinated patients (Total follow-up duration: 12 291.9 person-y) | Vaccinated patients (Total follow-up duration: 14 810.0 person-y) | aHR† (95% CI) | ||
|---|---|---|---|---|---|
| No. of patients with stroke | Incidence Rate (per 1000 person-y) (95% CI) | No. of patients with stroke | Incidence rate (per 1000 person-y) (95% CI) | ||
| Whole cohort | |||||
| Influenza season | 286 | 2326.7 (2057.1, 2596.4) | 284 | 1917.6 (1694.6, 2140.7) | 0.59 (0.50, 0.71)*** |
| Noninfluenza season | 222 | 1806.1 (1568.5, 2043.6) | 174 | 1174.9 (1000.3, 1349.5) | 0.50 (0.40, 0.61)*** |
| All seasons | 508 | 4132.8 (3773.4, 4492.2) | 458 | 3092.5 (2809.3, 3375.7) | 0.55 (0.48, 0.63)*** |
| Age, 55–64 ya | |||||
| Influenza season | 60 | 1200.5 (896.7, 1504.3) | 31 | 1286.8 (833.8, 1739.8) | 0.80 (0.51, 1.25) |
| Noninfluenza season | 42 | 840.4 (586.2, 1094.5) | 12 | 498.1 (216.3, 780.0) | 0.52 (0.27, 1.00)* |
| All seasons | 102 | 2040.9 (1644.8, 2436.9) | 43 | 1785.0 (1251.4, 2318.5) | 0.69 (0.48, 0.99)* |
| Age, 65–74 yb | |||||
| Influenza season | 75 | 2217.8 (1715.9, 2719.8) | 121 | 1793.6 (1474.0, 2113.2) | 0.55 (0.41, 0.75)*** |
| Noninfluenza season | 70 | 2070.0 (1585.0, 2554.9) | 71 | 1052.5 (807.6, 1297.3) | 0.41 (0.29, 0.57)*** |
| All seasons | 145 | 4287.8 (3589.9, 4985.7) | 192 | 2846.1 (2443.5, 3248.7) | 0.48 (0.39, 0.61)*** |
| Age, ≥75 yc | |||||
| Influenza season | 151 | 3859.6 (3244.0, 4475.2) | 132 | 2334.3 (1936.0, 2732.5) | 0.49 (0.39, 0.63)*** |
| Noninfluenza season | 110 | 2811.6 (2286.2, 3337.1) | 91 | 1609.2 (1278.6, 1939.9) | 0.47 (0.35, 0.62)*** |
| All seasons | 261 | 6671.3 (5861.9, 7480.6) | 223 | 3943.5 (3425.9, 4461.1) | 0.45 (0.40, 0.53)*** |
| Womend | |||||
| Influenza season | 153 | 2625.7 (2209.6, 3041.7) | 122 | 1772.1 (1457.6, 2086.5) | 0.49 (0.38, 0.63)*** |
| Noninfluenza season | 107 | 1836.2 (1488.3, 2184.2) | 85 | 1234.6 (972.2, 1497.1) | 0.53 (0.39, 0.72)*** |
| All seasons | 260 | 4461.9 (3919.5, 5004.3) | 207 | 3006.7 (2597.1, 3416.3) | 0.51 (0.42, 0.61)*** |
| Mene | |||||
| Influenza season | 133 | 2057.3 (1707.7, 2407.0) | 162 | 2044.1 (1729.3, 2358.8) | 0.74 (0.58, 0.95)* |
| Noninfluenza season | 115 | 1778.9 (1453.8, 2104.0) | 89 | 1123.0 (889.7, 1356.3) | 0.46 (0.34, 0.62)*** |
| All seasons | 248 | 3836.2 (3358.8, 4313.7) | 251 | 3167.0 (2775.2, 3558.8) | 0.61 (0.50, 0.74)*** |
*P < 0.05 **P < 0.01 ***P < 0.001
aTotal follow-up durations: 4997.9 and 2409.0 person-y for unvaccinated and vaccinated patients, respectively.
bTotal follow-up durations: 3381.7 and 6746.1 person-y for unvaccinated and vaccinated patients, respectively.
cTotal follow-up durations: 3912.3 and 5654.9 person-y for unvaccinated and vaccinated patients, respectively.
dTotal follow-up durations: 5827.1 and 6884.6 person-y for unvaccinated and vaccinated patients, respectively.
eTotal follow-up durations: 6464.7 and 7925.4 person-y for unvaccinated and vaccinated patients, respectively.
CI: confidence interval
HR: hazard ratio
aHR: adjusted hazard ratio
†The main model was adjusted for age; sex; Charlson comorbidity index; comorbidities of diabetes, hypertension, dyslipidemia, congestive heart failure, vascular disease, pneumonia, and dialysis; urbanization level; and monthly income by using propensity scores.