# Effect of Influenza Vaccination on Mortality and Heart Failure Hospitalization in Heart Failure Patients

## TL;DR

This study found that influenza vaccination in heart failure patients in Thailand was linked to fewer hospitalizations for heart failure but not to lower mortality.

## Contribution

The study provides new evidence on the impact of influenza vaccination on heart failure outcomes in a Thai population.

## Key findings

- Influenza vaccination was associated with a 56% reduction in the risk of heart failure hospitalization or death in unadjusted analysis.
- After adjusting for confounders, vaccination was linked to a reduced risk of heart failure hospitalization but not all-cause mortality.
- The adjusted analysis showed a 3.06-year longer time to event for heart failure hospitalization in vaccinated patients.

## Abstract

Background: The association of influenza vaccination and heart failure (HF) hospitalization and mortality in Thai HF patients is unknown. Objective: We wished to investigate associations between receiving an influenza vaccine and all-cause death or HF hospitalization in HF patients. Methods: We retrospectively reviewed medical records from two large tertiary-care centers in Thailand (Ramathibodi Hospital and Maharaj Nakorn Chiang Mai Hospital) with newly diagnosed heart failure between 2013 and 2020 in an outpatient clinic. We examined the relationship between influenza vaccination and outcomes in a propensity-adjusted model. Results: Of 588 patients, 181 (31%) received an influenza vaccination. During a median follow-up of 57 months, influenza vaccination was associated with a 56% reduction in the risk of HF hospitalization or death (HF hospitalization or all-cause death: HR: 0.44; 95% CI: 0.31–0.63; p < 0.001) in an unadjusted analysis. After propensity score adjustment, influenza vaccination, however, was not associated with a reduced risk of all-cause death but was associated with a reduced risk of HF hospitalization (ATE: 3.06 years; 95% CI: 0.14 to 5.98; p = 0.04). Conclusions: In patients with HF, influenza vaccination was not associated with a reduced risk of the composite of all-cause death or HF hospitalization after adjustment for confounders.