Influenza vaccination and risk of hospitalization in patients with heart failure: a self-controlled case series study.

AIMS: Evidence supporting yearly influenza vaccination in patients with chronic heart failure (HF) is limited, consequently leading to inconsistent guideline recommendations. We aimed to investigate the impact of influenza vaccination on the risk of hospitalization in HF patients. METHODS AND RESULTS: We used linked primary and secondary health records in England between 1990 and 2013. Using a self-controlled case series design with conditional Poisson regression, we estimated the incidence rate ratio (IRR, 95% CI) of the number of hospitalizations in a year following vaccination with an adjacent vaccination-free year in the same individuals. We found the uptake of vaccination to be varied and generally low (49% in 2013). Among 59,202 HF patients, influenza vaccination was associated with a lower risk of hospitalization due to cardiovascular disease (0.73 [0.71, 0.76]), with more modest effects for hospitalization due to respiratory infections (0.83 [0.77, 0.90]), and all-cause hospitalizations (0.96 [0.95, 0.98]). The relative effects were somewhat greater in younger patients but with no material difference between men and women. In validation analyses, effects were not significant for consecutive years without vaccination (0.96 [0.92, 1.00]) or hospitalization due to cancer (1.02 [0.84, 1.22]). CONCLUSION: In HF patients, influenza vaccination is associated with reduced risk of hospitalizations, especially for cardiovascular disease. Improved efforts for wider uptake of vaccination among HF patients are needed.