Association between influenza vaccine effectiveness and chronic diseases among older adults with dementia

This retrospective cohort study aimed to assess whether influenza vaccination reduces hospitalization rates and morbidity such as pneumonia incidence among older adults aged 80 years and above with severe dementia. Participants were grouped according to their influenza vaccination status. The primary outcomes evaluated included hospitalization rates, pneumonia incidence, and antibiotic use. Logistic regression models were used to predict pneumonia, and hospitalizations by the primary demographic and clinical characteristics. A total of 2,052 individuals were included in this study. Unvaccinated older adult patients had the lowest risk of being diagnosed with pneumonia and hospitalization. Female sex and Unvaccinated status were protective factors (OR = 0.389, 95%CI = 0.206, 0.733). The expected protective effects of the vaccine on pneumonia incidence and hospitalization may be less pronounced among older adults living with dementia. There is a need for more tailored influenza vaccination strategies for older adults with severe dementia and comorbid conditions.