Background and aims: The aim of this study was to determine the complications of influenza in all adults hospitalized with this disease and, specifically, to analyze the characteristics of post-infection cardiovascular events.

Methods: This work is observational descriptive study of adults hospitalized with influenza during the 2017-2018 and 2018-2019 seasons using the specific registry of a tertiary hospital. The complications analyzed were pneumonia, multiple organ dysfunction syndrome, septic shock, acute respiratory distress syndrome, and cardiac events.

Results: A total of 928 adults with influenza required hospitalization and 303 (32.7%) presented with one or more complications. A post-influenza cardiac event occurred in 2.5% of patients; they had a higher probability of ICU admission and higher mortality. Influenza vaccination was a protective factor for cardiac events (OR 0.32; 95%CI 0.13-0.83).

Conclusions: Influenza can lead to important complications in hospitalized patients. The high mortality rate associated with post-infection cardiac events means that preventive measures, including annual influenza vaccination, need to be emphasized.