Determinants of influenza vaccination uptake in older adults: findings from a retrospective cross-sectional study

OBJECTIVES: Influenza poses a serious health risk to older adults, and although annual vaccination is the most effective prevention, coverage in this population remains inconsistent. This study assessed influenza vaccination uptake and its predictors in this population. METHODS: A retrospective cross-sectional study was conducted among all patients aged ≥65 years during the 2022-2023 influenza season at a large Health Maintenance Organization. Data from a unified electronic medical record system included demographics, comorbidities, healthcare utilization, and influenza vaccination status. Logistic regression was used to identify independent predictors of vaccine uptake. RESULTS: Of 302,815 eligible older adults, 160,929 (53.2%) received an influenza vaccine in 2022-2023. Vaccinated individuals were older, had higher socioeconomic status, and a greater burden of comorbidities, including diabetes, hypertension, cardiovascular disease, chronic obstructive pulmonary disease, chronic kidney disease, inflammatory bowel disease, immunosuppression, and frailty-related conditions (frailty, high risk of falls, osteoporosis, and homebound status), while dementia was less prevalent. They also had more primary care physician (PCP) visits and higher prior-season vaccination rates (88.1% vs. 17.6%). In multivariate analysis, prior-year vaccination was the strongest predictor of vaccine uptake (OR:30.1; 95% CI:29.5-30.7). Frequent visits to PCPs were associated with higher vaccination rates (OR:1.86; 95% CI:1.71-2.02 for 1-3 visits; OR:2.82; 95% CI:2.62-3.04 for ≥4 visits). Dementia was negatively associated with vaccination (OR:0.78: 95% CI:0.75-0.81). In a sub-analysis of 191,668 individuals with an identified spouse, spousal vaccination was strongly predictive of patient vaccination (OR:8.33; 95% CI:8.09-8.57). CONCLUSIONS: Influenza vaccination in older adults is strongly associated with prior-year vaccination, PCP engagement, and spousal vaccination, and negatively associated with dementia. Targeted strategies to initiate vaccination, support patients with cognitive decline, and leverage household influence are needed to improve coverage among this vulnerable population.