Effect of seasonal influenza and COVID-19 vaccination on severity and long-term outcomes of patients with heart failure decompensations.

Aims: To investigate whether seasonal influenza and COVID-19 vaccinations influence the severity of decompensations and long-term outcomes of patients with acute heart failure (AHF).

Methods and results: We included consecutive AHF patients attended at 40 Spanish emergency departments during November and December 2022. They were grouped according to whether they had received seasonal influenza and COVID-19 vaccination. The severity of heart failure (HF) decompensation was assessed with the MEESSI scale, need for hospitalization, intensive care unit (ICU) admission, and in-hospital mortality. Long-term outcomes were 90-day and 1-year all-cause mortality. Associations between vaccination, HF decompensation severity, and long-term outcomes were investigated. Subgroup analyses were executed for 16 patient characteristics and their relationship with vaccination and 1-year mortality. We analysed 4243 patients (median age 85 years; interquartile range 77-90; 57% female): 1841 (43%) had received influenza vaccination, 3139 (74%) COVID-19 vaccination, 1773 (41.8%) received both vaccines (full vaccination) and 1036 (24.4%) none. Previous episodes of AHF, chronic obstructive pulmonary disease and chronic treatment with diuretics were associated with vaccination (either influenza, COVID-19 and full vaccination). High or very-high risk decompensation occurred in 18.6%; hospitalization in 72.3%, ICU admission in 1.1%, and in-hospital mortality in 8.4%. Influenza vaccination was associated with lower hospitalization rates (adjusted odds ratio [OR] 0.746, 95% confidence interval [CI] 0.636-0.876) and in-hospital mortality (OR 0.761, 95% CI 0.583-0.992), while COVID-19 vaccination was associated with increased hospitalizations (OR 1.215, 95% CI 1.016-1.454). Overall, 90-day and 1-year mortality were 20.3% and 34.4%. Both were decreased in influenza-vaccinated patients (adjusted hazard ratio [HR] 0.831, 95% CI 0.709-0.973; and HR 0.885, 95% CI 0.785-0.999, respectively) but only at 90 days in COVID-19 vaccinated patients (HR 0.829, 95% CI 0.702-0.980). Full vaccination achieved even greater reductions in in-hospital, 90-day, and 1-year mortality (HR 0.638, 95% CI 0.479-0.851; HR 0.702, 95% CI 0.592-0.833; and HR 0.815, 95% CI 0.713-0.931, respectively). Subgroup analysis based on patient-related characteristics demonstrated the consistence of vaccination with long-term survival.

Conclusion: In HF patients, seasonal influenza vaccination appears to be associated with less severe decompensation and lower 1-year mortality, while no firm conclusions can be drawn from the results of the present study regarding the benefits of COVID-19 vaccination. Full vaccination is associated with the greatest reduction in short- and long-term mortality.