Table 3.
Estimated vaccine effectiveness against the variant of concern (either the Delta or Omicron variant), stratified by age group (≤ 45 years; > 45 years), and analyzed by type of vaccination (BBIBO-CoV) and vaccination status (BNT162b2).
| Variant | Age group | Type of vaccination | Non-hospitalized | Hospitalized | Crude OR (95% CI) |
p-value | Adjusted OR (95% CI) | p-value | Vaccine effectiveness (95% CI) |
|---|---|---|---|---|---|---|---|---|---|
| Delta | ≤ 45 years |
BBIBP-CoV
Partially vaccinated Fully vaccinated |
81 (8.0%) 936 (92%) |
11 (42.3%) 15 (57.7%) |
1.28 (0.58 to 2.30) 0.15 (0.09 to 0.27) |
0.46 < 0.001 |
0.88 (0.43 to 1.79) 0.06 (0.03 to 0.10) |
0.45 < 0.001 |
24% (–56% to 64%) 94% (90% to 97%) |
|
BNT162b2
Partially vaccinated Fully vaccinated |
26 (21.8%) 93 (78.2%) |
1 (50%) 1 (50%) |
0.36 (0.04 to 2.69) 0.10 (0.01 to 0.73) |
0.32 0.02 |
0.24 (0.03 to 1.91) 0.05 (0.01 to 0.42) |
0.18 0.01 |
76% (NA to 97%) 95% (58% to 99%) |
||
| > 45 years |
BBIBP-CoV
Partially vaccinated Fully vaccinated |
14 (4.3%) 314 (95.7%) |
28 (38.9%) 44 (61.1%) |
1.17 (0.59 to 2.30) 0.08 (0.05 to 0.12) |
0.64 < 0.001 |
1.27 (0.62 to 2.65) 0.08 (0.05 to 0.12) |
0.51 < 0.001 |
NA 92% (88% to 95%) |
|
|
BNT162b2
Partially vaccinated Fully vaccinated |
7 (25.9%) 20 (74.1%) |
3 (75%) 1 (25%) |
0.25 (0.06 to 0.98) 0.02 (0.0 to 0.22) |
0.04 0.001 |
0.18 (0.04 to 0.80) 0.02 (0.004 to 0.22) |
0.02 0.001 |
82% (20% to 96%) 98% (78% to 99.6%) |
||
| Omicron | ≤ 45 years |
BBIBP-CoV
Partially vaccinated Fully vaccinated |
4 (2.0%) 193 (98%) |
0 (0.0%) 8 (100%) |
NA 0.11 (0.05 to 0.26) |
NA < 0.001 |
NA 0.10 (0.04 to 0.26) |
NA < 0.001 |
NA 90% (74% to 96%) |
|
BNT162b2
Partially vaccinated Full vaccinated |
4 (8.2%) 45 (91.8%) |
0 (0.0%) 1 (100%) |
NA 0.06 (0.01 to 0.46) |
NA 0.007 |
NA 0.06 (0.01 to 0.47) |
NA 0.01 |
NA 94% (53% to 99%) |
||
| > 45 years |
BBIBP-CoV
Partially vaccinated Full vaccination |
2 (3.2%) 61 (96.8%) |
1 (7.1%) 13 (92.9%) |
0.60 (0.04 to 7.63) 0.25 (0.09 to 0.71) |
0.69 0.01 |
0.37 (0.02 to 5.87) 0.42 (0.13 to 1.33) |
0.48 0.14 |
63% (NA to 98%) 58% (NA to 87%) |
|
|
BNT162b2
Partial Vaccination Full vaccination |
0 (0.0%) 5 (100%) |
0 (0.0%) 1 (100%) |
NA 0.24 (0.02 to 2.41) |
NA 0.22 |
NA 0.17 (0.01 to 2.23) |
NA 0.18 |
NA 83% (NA to 99%) |
CI, confidence interval; NA, not applicable; OR, odds ratio.
Reference categories: unvaccinated.
Stratified by lineage and the ≤ 45 years and > 45 years age groups.
Chi-squared test of significance was used to measure associations between reference category and each category in the model.
Bivariate analysis (non-hospitalized vs. hospitalized) was used for the regression models, presented as crude OR and adjusted OR for nationality and sex.
Vaccine effectiveness estimation was adjusted for the covariates, that is, nationality and sex, and calculated from the regression model [(1 − OR) * 100] and expressed as a percentage.