Effectiveness of Influenza Vaccination Among Older Adults Across Kidney Function: Pooled Analysis of 2005-2006 Through 2014-2015 Influenza Seasons

Rationale & Objective: Influenza vaccination is recommended for all adults but particularly for older adults and those with high-risk conditions. Reduced kidney function is an important high-risk condition, but the effectiveness of influenza vaccination across kidney function is uncharacterized. We assessed the effectiveness of influenza vaccination among older adults with and without reduced kidney function. Study Design: Observational cohort study. Setting & Participants: 454,634 person-seasons among 110,968 individuals 65 years or older in the Geisinger Health System between the 2005 and 2015 influenza seasons, with baseline characteristics matched between those with and without vaccination using inverse probability weighting. Exposures: Status of influenza vaccination. Outcomes: Incident hospitalization with pneumonia/influenza, coronary heart disease, and heart failure during influenza season stratified by estimated glomerular filtration rate (eGFR; ≥ 60, 30-59, and < 30 mL/min/1.73 m²). Analytical Approach: Pooled logistic regression analysis to estimate adjusted ORs. Results: In the 2014-2015 influenza season, the prevalence of influenza vaccination was 63.3% without evident difference across eGFR categories. The incidence of hospitalization was higher in lower eGFRs (eg, 2.2% per person-season among those not vaccinated with eGFR < 30 vs 0.7% with ≥ 60 mL/min/1.73 m² for pneumonia/influenza). Overall, influenza vaccination was associated with lower odds of hospitalization with pneumonia/influenza (OR, 0.86; 95% CI, 0.79-0.93), coronary heart disease (OR, 0.93; 95% CI, 0.88-0.97), and heart failure (OR, 0.92; 95% CI, 0.86-0.99). When assessing by eGFR categories, the association was consistent in eGFR ≥ 30, but not significant in < 30 mL/min/1.73 m² (ORs of 1.04 [95% CI, 0.79-1.36] for pneumonia/influenza, 1.03 [95% CI, 0.87-1.23] for coronary heart disease, and 1.10 [95% CI, 0.92-1.33] for heart failure). Limitations: Possible unmeasured confounding. Conclusions: Influenza vaccination was associated with lower risk for hospitalizations with pneumonia/influenza and major cardiac diseases in eGFR ≥ 30 mL/min/1.73 m². Studies are needed to explore optimal vaccination strategies for eGFR < 30 mL/min/1.73 m².