(A-336) Regional differences in COVID-19 vaccine uptake and their determinants among Swedish older adults

Background: In 2023, COVID-19 vaccine uptake decreased, and the variation increased across Swedish regions, warranting further investigation to ensure equitable vaccine coverage, especially among vulnerable groups. Reasons for regional differences in vaccine uptake could reveal potential threats to vaccination efforts.

Objectives: To investigate factors contributing to regional variation in COVID-19 vaccination throughout the pandemic among adults ≥65 years in Sweden.

Methods: This Swedish nationwide register-based cohort study, which lasted from 27 December 2020 to 31 January 2024, comprised over 2 million older adults. Its outcomes were the uptake of different doses of the COVID-19 vaccine throughout the pandemic, focusing on the first dose (measuring the initial response to the pandemic), the sixth dose (indicating the ongoing sequenced vaccination efforts), and the 2023 autumn booster (representing the shift to routine annual vaccination ahead of the autumn/winter season).
Regional age- and sex-standardized vaccine uptake rates over these periods were calculated. Potential predictors, including individual-level sociodemographic characteristics, healthcare utilization, overall health condition, and regional-level socioeconomic factors, were assessed using mixed-effects Poisson regression to identify associations to vaccine uptake.

Results: The overall uptake by 31 Jan 2024 was 95% for the first dose, 66% for the sixth, and 73% for the autumn booster. The time trend for uptake of the first dose was similar among the 21 Swedish regions. However, larger, more populous regions showed slower uptake and lower coverage as the vaccinations progressed, especially for the sequential doses administered and the 2023 autumn booster. Vaccine uptake was primarily driven by individual-level sociodemographic factors. Younger age, male sex, being born outside of Sweden, lower income, lower education level, and living alone were associated with lower uptake. Regional-level factors, such as infrastructure and socioeconomic conditions, had minimal impact. This pattern was similar across all doses investigated.

Conclusions: Regional differences in COVID-19 vaccine uptake became more pronounced for subsequent doses as national prioritization and coordination were relaxed. Our findings highlight potential challenges in decentralized healthcare systems, where regional inequalities may contribute to disparities in vaccine access and other essential healthcare services. In addition, persistent socioeconomic and demographic disparities underscore the need for targeted interventions, including education and outreach, to ensure equitable vaccine coverage across all population groups and geographies.