Effectiveness of influenza vaccination in elderly diabetic patients: A retrospective cohort study

Purpose: Studies regarding the clinical benefits of influenza vaccination in diabetic patients are limited. This study evaluated if the elderly diabetic patients who have had influenza vaccination would have benefits such as reduced medical care and mortality. Methods: We used the universal insurance claims data from 2001 to 2009 in Taiwan to identify annual elderly patients with diabetes cohorts with (N=4454) and without (N=4571) influenza vaccination. The risk of developing pneumonia or influenza, respiratory failure, intensive care, hospitalization, and mortality were measured and compared between cohorts within one year of follow-up. Results: The vaccine cohort had lower incidences of pneumonia or influenza and respiratory failure compared with the non-vaccine cohort. More importantly, the vaccine cohort had a hospitalization rate that was 11% less than the non-vaccine cohort (29.6 vs. 33.1 per 100 person-years) with an adjusted hazard ratio (HR) of 0.88 (95% CI 0.81-0.96). The vaccine cohort was also less likely to be admitted to the intensive care unit (ICU) [0.58 vs. 2.05 per 100 person-year; adjusted HR 0.30 (95% CI 0.19-0.47)] and less likely to expire [3.13 vs. 7.96 per 100 person-year; adjusted HR 0.44 (95% CI 0.36-0.54)]. Influenza vaccination reduced the hospitalization cost by 1282.6 USD, compared with patients without influenza vaccination (95% CI -2210.3, -354.8). Conclusion: Influenza vaccination is associated with a reduced risk of morbidity, hospitalization, ICU admissions, and mortality. In addition, the hospitalization cost is reduced.