ABSTRACT: COVID-19 Vaccination Dynamics in the US: A Follow-up Study

Concerns regarding Coronavirus disease 2019 (COVID-19) disparities among the vulnerable populations have been studied widely and extend to vaccine allocation. With the current status of the pandemic, emergence of new variants, and recommendations toward the administration of third and fourth booster shots, understanding the population-level vaccine coverage status is critical for achieving equity in public health outcomes. In a previous population-level study focused on California counties, using the data from U.S. Census Bureau, Agency for Toxic Substances and Disease Registry (ATSDR), California Health & Human Services Agency (CHHS), and Centers for Disease Control and Prevention (CDC), we investigated the scope of vaccine inequity. In this research, we modeled the trends of vaccination using the Social Vulnerability Index (SVI) and its four components, including "socioeconomic status," "household composition and disability," "minority status and language," and "housing type and transportation." Growth velocity and anticipated maximum proportion of the vaccinated population were modeled based on 9228 data points of daily vaccination numbers from December 15, 2020, to May 23, 2021, SVI, and its four themes. We reported that although vaccination coverage was significantly lower in high vulnerability counties, they are estimated to achieve a higher proportion of vaccinated individuals eventually, particularly based on SVI Theme 3, while predicting that disparities in vaccination rates decrease over time.