Table 3.
Risk of intensive care unit admission or in-hospital death among individuals hospitalised with influenza, by influenza vaccination status and influenza virus type and subtype
|
Children aged 6–24 months |
Adults aged 18–64 years with pre-existing medical conditions |
Older adults aged ≥65 years | |||||
|---|---|---|---|---|---|---|---|
| Unvaccinated | Partially vaccinated | Fully vaccinated | Unvaccinated | Vaccinated | Unvaccinated | Vaccinated | |
| Influenza A(H3N2), 2013–19 | |||||||
| n/N (%) | 15/126 (11·9%) | 11/76 (14·5%) | 3/26 (11·5%) | 52/173 (30·1%) | 17/53 (32·1%) | 113/522 (21·6%) | 78/348 (22·4%) |
| OR (95% CI) | 1 (ref) | 1·25 (0·54–2·90) | 0·97 (0·26–3·63) | 1 (ref) | 1·10 (0·56–2·14) | 1 (ref) | 1·04 (0·75–1·45) |
| aOR (95% CI) | 1 (ref) | 1·29 (0·71–2·33) | 1·05 (0·41–2·70) | 1 (ref) | 1·49 (0·99–2·24) | 1 (ref) | 0·98 (0·76–1·27) |
| Influenza A(H3N2), 2013–19 (excluding 2014 and 2017) | |||||||
| n/N (%) | 9/76 (11·8%) | 6/44 (13·6%) | 3/13 (23·1%) | 21/82 (25·6%) | 5/28 (17·9%) | 58/259 (22·4%) | 44/188 (23·4%) |
| OR (95% CI) | 1 (ref) | 1·17 (0·38–3·59) | NE | 1 (ref) | 0·63 (0·21–1·89) | 1 (ref) | 1·06 (0·68–1·66) |
| aOR (95% CI) | 1 (ref) | 1·28 (0·57–2·88) | NE | 1 (ref) | 0·53 (0·17–1·71) | 1 (ref) | 1·13 (0·80–1·61) |
| Influenza A(H1N1), 2013–19 | |||||||
| n/N (%) | 29/169 (17·1%) | 9/74 (12·2%) | 2/27 (7·4%) | 66/188 (35·1%) | 12/50 (24·0%) | 107/316 (33·9%) | 38/162 (23·5%) |
| OR (95% CI) | 1 (ref) | 0·67 (0·30–1·50) | 0·39 (0·09–1·73) | 1 (ref) | 0·58 (0·28–1·20) | 1 (ref) | 0·60 (0·39–0·92)* |
| aOR (95% CI) | 1 (ref) | 0·40 (0·21–0·74)* | 0·38 (0·12–1·19) | 1 (ref) | 0·53 (0·32–0·88)* | 1 (ref) | 0·75 (0·56–1·01) |
| Influenza B, 2013–19 | |||||||
| n/N (%) | 10/75 (13·3%) | 4/36 (11·1%) | 1/14 (7·1%) | 9/41 (21·9%) | 3/15 (20·0%) | 33/116 (28·4%) | 16/90 (17·8%) |
| OR (95% CI) | 1 (ref) | 0·81 (0·23–2·83) | 0·50 (0·06–4·34) | 1 (ref) | 0·89 (0·20–3·98) | 1 (ref) | 0·54 (0·28–1·07) |
| aOR (95% CI) | 1 (ref) | 0·40 (0·14–1·11) | 0·32 (0·06–1·61) | 1 (ref) | 1·01 (0·21–4·89) | 1 (ref) | 0·58 (0·34–0·98)* |
To calculate aORs, logistic regression models were weighted by inverse probability treatment weights and adjusted for antiviral medication use, duration of illness at admission, and calendar week (fit as a cubic spline); pooled ORs were calculated using the pool() function in R, which averages the estimates across the 20 imputed datasets and calculates total variance across the repeated analyses using Rubin's rule. OR=odds ratio. aOR=adjusted odds ratio. NE=not estimated (insufficient data).
95% CI does not overlap with 1 (significant difference compared with reference category).