Table 2.
Summary of the effectiveness of 3-dose inactivated vaccine, versus 2-dose (reference level), against SARS-CoV-2 Omicron BA.5 infection
| Sample size, n (column %) | Length of follow-up (person-day), median [IQR] | Incidence rate (per 100,000 person-day) | Vaccine effectiveness, estimate (95% CI) | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 2-dose vaccinee (ref.) | 3-dose vaccinee | |||||||||
| Test-positive | Test-negative | Test-positive | Test-negative | 2-dose | 3-dose | 2-dose | 3-dose | Crude | Adjusteda | |
| Overall | 34 (100%) | 3283 (100%) | 99 (100%) | 15,952 (100%) | 8 [7, 15] | 8 [7, 14] | 88.51 | 53.67 | 40.1% (11.4, 59.5) | 35.5% (2.0, 57.5) |
| Sex | ||||||||||
| Male | 16 (47.1%) | 1539 (46.9%) | 49 (49.5%) | 7399 (46.4%) | 9 [7, 17] | 9 [7, 16] | 85.05 | 54.37 | 35.8% (− 11.7, 63.6) | 39.7% (3.2, 62.5) |
| Female | 18 (52.9%) | 1744 (53.1%) | 50 (50.5%) | 8643 (54.2%) | 8 [7, 14] | 8 [7, 13] | 91.83 | 53.01 | 43.8% (3.4, 67.3) | 39.9% (6.6, 61.3) |
| Age stratification | ||||||||||
| Young adult: 18–39 yr | 11 (32.4%) | 1857 (56.6%) | 51 (51.5%) | 9262 (58.1%) | 8 [7, 13] | 8 [7, 13] | 53.74 | 49.15 | 7.0% (− 44.0, 51.6) | 40.2% (4.8, 62.5) |
| Middle-age adult: 40–59 yr | 8 (23.5%) | 843 (25.7%) | 30 (30.3%) | 4241 (26.6%) | 9 [7, 17] | 9 [7, 16] | 76.72 | 58.80 | 25.5% (− 38.7, 65.9) | 33.2% (− 8.9, 59.3) |
| Old-age adult: 60+ yr | 15 (44.1%) | 583 (17.8%) | 18 (18.2%) | 2449 (15.4%) | 9 [7, 18] | 8 [7, 15] | 199.55 | 60.66 | 71.4% (43.0, 85.7) | 37.8% (− 10.1, 65.2) |
| Lag from last vaccine to be exposed | ||||||||||
| 15–180 d | 15 (44.1%) | 1208 (36.8%) | 15 (15.2%) | 3594 (22.5%) | 8 [7, 14] | 8 [7, 13] | 107.61 | 37.69 | 66.4% (31.0, 83.6) | 60.2% (22.8, 79.5) |
| 181+ d | 19 (55.9%) | 2075 (63.2%) | 84 (84.8%) | 12,358 (77.5%) | 8 [7, 15] | 9 [7, 15] | 77.63 | 58.07 | 25.8% (− 18.3, 55.0) | 35.0% (2.8, 56.5) |
| Vaccine status of source case | ||||||||||
| 0–1 dose | 3 (8.8%) | 258 (7.9%) | 12 (12.1%) | 1118 (7.0%) | 14 [6, 22] | 13 [6, 22] | 76.22 | 73.91 | 7.7% (− 69.7, 74.1) | 29.2% (− 30.8, 65.3) |
| 2 doses | 10 (29.4%) | 397 (12.1%) | 20 (20.2%) | 1861 (11.7%) | 10 [6, 23] | 10 [6, 23] | 172.27 | 74.89 | 57.3% (8.1, 80.2) | 31.4% (− 27.5, 65.9) |
| 3 doses | 21 (61.8%) | 2628 (80.0%) | 67 (67.7%) | 12,973 (81.3%) | 8 [7, 13] | 8 [7, 12] | 73.24 | 47.35 | 35.4% (− 5.4, 60.5) | 39.9% (6.7, 61.3) |
aThe vaccine effectiveness (VE) was estimated from multivariate conditional logistic regression model adjusted for covariables including sex, age, epidemiological week of 2022, contact setting, and vaccine status of source case