Impact of influenza vaccination on in-hospital outcomes among patients with heart failure and acute respiratory illness

Influenza vaccination is recommended to patients with heart failure (HF), who are vulnerable to severe complications from respiratory infections. However, data on its impacts on in-hospital outcomes remain limited. We analyzed the National Inpatient Sample (2018 to 2020), including adults (≥ 18 years) hospitalized with acute respiratory infection (ARI) and HF, identified using ICD-10 CM Codes(ARI: J09.x–J11.x, J12.x–J18.x, J20.x, J21.x; HF: I50.x, I0981, I110, I130, I132, I97130, I97131, O29121–O29129, Z95811, Z95812). The primary outcome was in-hospital mortality. Secondary outcomes included mechanical ventilation use, sepsis, length of stay (LOS) in hospital, and inflation-adjusted total hospital charges. Multivariable logistic and linear regression models assessed associations between influenza vaccination and outcomes, adjusting for demographic, clinical, socioeconomic and hospital-level factors. Among 491,210 hospitalizations for patients with HF and ARI, 28% (137,538) received influenza vaccination. Vaccinated patients with HF had significantly lower odds of in-hospital mortality (OR: 0.32; 95% CI, 0.23–0.46; p < 0.001), mechanical ventilation (OR: 0.67; 95% CI, 0.54–0.83; p < 0.001), and sepsis (OR: 0.63; 95% CI, 0.45–0.88; p = 0.006). They also had lower total hospital charges (β = −$3181; 95% CI, −$5264 to –$1098; p = 0.003). No significant difference was found in LOS (β = −0.05; 95% CI, −0.21 to 0.12; p = 0.6). Influenza vaccination for ARI is linked to lower mortality, fewer complications, and reduced health care costs. These findings support the promotion of inpatient vaccination to improve outcomes and reduce burden in the high-risk population.