•This study investigates the effects of state-level predictors on changes in COVID-19 vaccination rates, Apr 2021-Jan 2022.•Analyses of panel data show Biden’s approval and COVID-19 death are positively associated with the growing vaccination rate.•Inflation and economic recovery are negatively associated with the vaccination rate during this period.•COVID-19 mortality has a more substantial impact on elevating the vaccination rate among states with stronger Biden’s approval.•The findings complement the literature and provide fresh insights to promote the vaccine rollout. The COVID-19 pandemic has brought an unprecedented impact on Americans for over three years. One effective strategy to mitigate the pandemic’s damage lies in the vaccine. This study aims to investigate the effects of state-level predictors that vary month-by-month on changes in vaccination rates. Panel data of state-level indicators are built for all 50 states from April 2021 to January 2022. The dependent variable is the monthly increase in vaccination rate, and the independent variables include measures of Biden’s approval, inflation, economic recovery, and COVID-19 mortality for each month of this study period. Fixed-effects regression is adopted for longitudinal statistical estimation. Findings show that over time Biden’s approval and COVID-19 death are positively associated with the growth in the vaccination rate, while inflation and economic recovery are negatively associated with the vaccination rate. Significant interactions are identified among these predictors. The findings from analyzing panel indicators at the state level complement the current literature dominated by examining cross-sectional data and provide public health officials with fresh insights to promote the vaccine rollout.