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

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.