hesitancy or refusal of current and future vaccines, decreasing the burden of communicable diseases. Supplementary—review and editing, R.S.P. and X.S. All authors have read and agreed to the published version of the manuscript. Funding: This research was funded by University of Arkansas for Medical Sciences Translational Research Institute funding awarded through the National Center for Research Resources and National Center for Advancing Translational Sciences of the National Institutes of Health (NIH) [UL1TR003107]. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH. Institutional Review Board Statement: The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Institutional Review Board at the University of Arkansas for Medical Sciences (IRB#261226). Informed Consent Statement: Respondents reviewed study and consent information at the beginning of the online survey, and consent was documented in REDCap. Data Availability Statement: The deidentified data underlying the results presented in this study may be made available upon request from the corresponding author Dr. Pearl A. McElfish, at pamelfish@uams.edu. The data are not publicly available in accordance with funding requirements and participant privacy. Conflicts of Interest: The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results. References 1. Stern, A.M.; Markel, H. The history of vaccines and immunization: Familiar patterns, new challenges. Health Aff. (Millwood) 2005, 24, 611–621. [CrossRef] 2. Rumfield, S.C.; Roller, N.; Pellom, S.T.; Schlom, J.; Jochems, C. Therapeutic vaccines for HPV-associated malignancies. Immunotargets 2020, 9, 167–200. [CrossRef] 3. MacDonald, N.E. Vaccine hesitancy: Definition, scope and determinants. Vaccine 2015, 33, 4161–4164. [CrossRef] Int. J. Environ. Res. Public Health 2021, 18, 8690 8 of 9 4. Berawi, M.A.; Suwartha, N.; Kusrini, E.; Yuwono, A.H.; Harwahyu, R.; Setiawan, As of mid-February 2021, more than 40 million US adults, over 12 percent of the total US population, have received at least one dose of a COVID-19 vaccine, and vaccine sites are administering more than 1.5 million doses (both first and second) daily. 1 Health officials estimate the US will achieve herd immunity when 70 to 90 percent of the population has been vaccinated or previously infected, after which virus transmission will slow significantly. 2 Early data show disparities in vaccination rates, with people of color receiving disproportionately fewer vaccine doses and facing greater barriers navigating the complicated systems for scheduling vaccine appointments and traveling to vaccination sites (Ndugga et al. 2021). 3 Eliminating disparities and reaching herd immunity will require addressing challenges in both vaccine supply (i.e., the limited number of doses and inequitable access to them) and demand (i.e., vaccine hesitancy). This study explores vaccine hesitancy4 among nonelderly adults with new data from the Urban Institute’s Well-Being and Basic Needs Survey (WBNS), a nationally representative survey of more than 7,500 adults ages 18 to 64 fielded December 8 through 30, 2020.5 We define vaccine-hesitant adults as those reporting they would probably not or definitely not get a COVID-19 vaccine. We note vaccine hesitancy exists along a continuum (SAGE Working Group 2014), and concerns that people hold at a point in time may change as new information becomes available about the vaccines’ effectiveness and potential side effects. F R Protecting the population from COVID-19 through vaccination requires understanding who is hesitant, what their concerns about the vaccines are, and who is best positioned to address them. This study examines how vaccine concerns, trust in community sources of information, and connections to the health care system vary by race, ethnicity, and political party affiliation, where some of the starkest differences in vaccine hesitancy are evident. We find the following: ◼ In December 2020, more than one-third of nonelderly adults reported they would probably not or definitely not get a COVID-19 vaccine. Nearly half of Black adults held this position, compared with about one-third of white and Hispanic/Latinx adults. However, almost twothirds of Black adults seemed to still be considering their decisions about getting the vaccine.i ◼ Though Black adults reported greater vaccine hesitancy for well-founded historical reasons, white adults are a larger subgroup of the population and, consequently, constituted 59 percent of all vaccine-hesitant nonelderly adults. ◼ Republicans were nearly twice as likely as Democrats to report they would probably not or definitely not get vaccinated (47 percent versus 25 percent). Differences in hesitancy by political affiliation were largest among white adults, followed by Hispanic/Latinx adults. ◼ Most vaccine-hesitant adults were concerned about side effects and vaccine effectiveness. However, more than half (57 percent) thought they did not need the vaccine, and 63 percent of vaccine-hesitant Republicans held this view. Other reasons for being hesitant