Uncertainties about COVID-19 vaccines and variants have been linked to vaccination refusal on a significant scale. To optimise public health communication on vaccination and inform vaccination policy, it is necessary to understand the substantive nature of these uncertainties. Our study, using a corpus of texts from 324 UK citizens, examines these uncertainties. The results suggest that major public uncertainties regarding COVID-19 vaccines are expressed in terms of: (1) concerns about the safety of the vaccines; (2) concerns about the effectiveness of the vaccines; (3) perceived lack of trustworthiness and/or competence of actors in the vaccination process; (4) concerns about the logistics of the vaccination roll-out; and (5) uncertainty about the longer-term need for vaccines and social consequences. Public uncertainties regarding COVID-19 are complex and will continue to evolve. Policy responses must be informed by an understanding of the factors that instigate and maintain uncertainties in individuals and the wider society.