Table 4. Unadjusted and adjusted risk factor associations for Influenza B Virus (IBV) detection* among patients with severe acute respiratory illness in the Hanoi area, 2017–2019.
| Risk factors | Total No. (%) | IBV+ n = 54 (%) | Unadjusted OR (95% CI)† | Adjusted‡ OR (95% CI) |
|---|---|---|---|---|
| Gender§ | ||||
| Male | 128 (36.8) | 22 (40.7) | 1.2 (0.6–2.3) | -- |
| Female | 217 (62.4) | 32 (59.3) | Reference | -- |
| Age quartiles (Q)‖ | ||||
| 15-24yrs (Q1) | 77 (25.5) | 8 (17.4) | Reference | -- |
| 25-34yrs (Q2) | 75 (24.8) | 12 (26.1) | 1.6 (0.6–4.9) | -- |
| 35-56yrs (Q3) | 79 (26.2) | 14 (30.4) | 1.9 (0.7–5.4) | -- |
| ≥ 57yrs (Q4) | 71 (23.5) | 12 (26.1) | 1.8 (0.6–5.3) | -- |
| Year of study enrollment | ||||
| 2017 | 210 (60.3) | 49 (90.7) | 6.0 (2.3–19.8) | 7.9 (2.7–22.9) |
| 2018 | 103 (29.6) | 5 (9.3) | Reference | Reference |
| 2019 | 35 (10.1) | -- | -- | -- |
| Hospital type | ||||
| Military | 151 (43.4) | 32 (59.3) | 2.1 (1.1–4.1) | -- |
| Civilian | 197 (56.6) | 22 (40.7) | Reference | -- |
*Influenza B virus detection by real-time RT-PCR with Ct value ≤ 38
†Exact confidence intervals
‡After stepwise, unconditional logistic regression using a saturated model and backward elimination of covariates with p > 0.05
§Gender data missing for some patients (n = 3) removed from calculations
‖Age data missing for some patients (n = 46) removed from calculations