Influenza vaccination and mortality among adults with heart failure in an integrated healthcare delivery system, 2009–2018

Abstract

Background: Influenza infection can result in decompensation or exacerbation of heart failure (HF) symptoms, hospitalization, and death. Objective: To examine the association of influenza vaccination with mortality and hospitalization during influenza and non-influenza seasons between 2009 and 2018. Design, Setting, and Participants: In this prospective, observational cohort study, we included Kaiser Permanente Southern California members with a HF diagnosis prior to September 1 each year from 2009 to 2017. Exposure: The first influenza vaccination in each season (September 1 to May 31) was recorded. Vaccinated/unvaccinated patients were matched 1:1 on age, sex, and ejection fraction at the vaccination date (n-total = 74,870). Main Outcomes: Patients were followed through the end of each influenza season for all-cause mortality. Secondary outcomes included cardiovascular mortality and all-cause hospitalization. In a sensitivity analysis, we examined mortality in the non-influenza season. Results: Influenza vaccinated vs unvaccinated patients had more comorbidities and higher healthcare utilization. After multivariable adjustment for utilization, sociodemographics, comorbidities, and medications, influenza vaccinated vs unvaccinated patients had a lower risk of all-cause mortality and cardiovascular mortality during the influenza season (hazard ratio [HR] 0.66, 95% confidence interval [CI] 0.63, 0.70 and HR 0.68, 95% CI 0.63, 0.74, respectively) but a higher risk of all-cause hospitalization (HR 1.27, 95% CI 1.21, 1.31). There was no association between influenza vaccination and all-cause or cardiovascular mortality during the non-influenza season (HR 0.99, 95% CI 0.89, 1.09 and HR 1.00, 95% CI 0.84, 1.21, respectively). Conclusions: Influenza vaccination in HF patients was associated with a lower risk of mortality during the influenza season. Our findings provide support for recommendations of universal influenza vaccination in patients with HF.