Regional differences in COVID-19 vaccine uptake and their determinants among Swedish older adults.

OBJECTIVES

Regional differences in vaccine uptake constitute a threat to vaccination efforts. This study investigated factors contributing to such variation in COVID-19 vaccination (throughout the pandemic, including first, sixth dose and a 2023 autumn booster) among adults ≥65 years in Sweden.

STUDY DESIGN

This Swedish nationwide register-based cohort study comprised over 2 million older adults. The study periods began on December 27, 2020 for the first dose, February 1, 2022 for the sixth dose, and October 1, 2023 for the seasonal booster dose, ending on January 31, 2024.

METHODS

We calculated regional age- and sex-standardized vaccine uptake rates over these periods. We used mixed-effects Poisson regression to identify associations between potential predictors (both individual- and regional-level sociodemographic and health-related factors) and vaccine uptake.

RESULTS

The overall uptake was 95 % for the first dose, 66 % for the sixth, and 73 % for the seasonal booster. The time trend for uptake of the first dose was similar among the 21 Swedish regions. However, for the sixth and booster doses, larger, more populous regions were slower and had lower uptake rates. Individual-level factors were stronger predictors for vaccine uptake than regional-level. Male sex, born outside of Sweden, having low income and low education were associated with lower uptakes.

CONCLUSIONS

Regional differences in vaccine uptake emerged for subsequent doses as national prioritization and coordination was relaxed. Our findings underscore the importance of minimizing regional variation through targeted interventions.