Abstract
Many countries continue to recommend COVID-19 vaccination, primarily to older adults. Following the transition of the national immunization program for COVID-19 vaccination in Japan in April 2024, implementation was delegated to municipalities. However, vaccination uptake and its associated factors, particularly municipal-level policies, remain unclear. This ecological study clarifies the factor associated with COVID-19 vaccination uptake among older adults aged ≥65 years in Japan during 2024-2025 by analyzing 1,740 municipalities. Municipal vaccination uptake among individuals aged ≥65 years was estimated from vaccine distribution data for the period. We examined the associations of uptake with municipal policies and sociodemographic factors using negative binomial regression, and incidence rate ratios (IRRs) and 95% confidence intervals (CIs) were calculated. The mean estimated vaccination uptake across Japan was 17.9%. Individual notification via mailed vaccine screening questionnaires had the largest effect, with higher uptake (IRR 1.57; 95% CI, 1.37-1.80). Low out-of-pocket expenses were also associated with higher uptake (IRR 1.31; 95% CI, 1.12-1.52 for ≤2,000 JPY, Reference: ≥3,001 JPY). A higher proportion of those aged ≥75 (IRR 1.03; 95% CI, 1.01-1.05) and a higher number of physicians (IRR 1.03; 95% CI, 1.00-1.06) were positively associated with uptake as well. Conversely, the area deprivation index was associated with lower uptake (IRR 0.87; 95% CI, 0.76-0.98). Proactive municipal strategies (individual notifications and subsidies to reduce out-of-pocket expenses) were significantly associated with increased vaccination uptake. To ensure equitable access and mitigate disparities, future vaccination campaigns should incorporate outreach measures to address socioeconomic barriers.