As of December 2020, 27% of the public says that they probably or definitely would not receive a COVID-19 vaccine, even if it were free and deemed safe by scientists. Reasons for hesitancy include worries about potential side effects, lack of trust in the government, concern that the vaccine is too new, and concern about the impact of politics on vaccine development. Barriers and challenges to disseminating information have also complicated efforts to vaccinate vulnerable populations. This briefing explored the current state of COVID-19 vaccine deployment efforts, cultural, historical, and political influences that may generate feelings of hesitancy, and how to ensure optimal vaccine uptake in key populations.