Association between influenza vaccination and hospitalisation or all-cause mortality, and all-cause mortality alone, in people with COVID-19 within the CHIA database cohort (n=6921)
| Outcome | Model specification | OR (95% CI) | P value |
| Hospitalisation or all-cause mortality | Unadjusted | 1.39 (1.26 to 1.53) | <0.001 |
| Stabilised IPTW* | 0.85 (0.75 to 0.97) | 0.020 | |
| Stratification and pooling | 0.87 (0.78 to 0.98) | 0.021 | |
| All-cause mortality | Unadjusted | 1.13 (0.98 to 1.30) | 0.097 |
| Stabilised IPTW† | 0.76 (0.64 to 0.90) | 0.001 | |
| Stratification and pooling | 0.59 (0.51 to 0.69) | <0.001 |
*IPTW: inverse probability of treatment weighting based on the propensity score for influenza vaccination stabilised by the marginal probability of vaccination in the study population.
†The propensity score was divided into deciles, and the OR for the association between influenza vaccination and the outcome was estimated in each of the deciles. Mantel-Haenszel-weighted pooled OR was estimated using Woolf approximation for the calculation of SE.
CHIA, Care and Health Information Analytics.