Patients in medium secure hospitals may be at particularly increased risk of coronavirus disease 2019 (COVID-19) infection and complications. We undertook a service evaluation involving all current in-patients within a single, English medium secure hospital to describe the uptake of the COVID-19 vaccine among this population. Data regarding capacity to consent to the vaccine, acceptance/refusal of this (and reasons for refusal) and demographics was retrospectively collected from the patients’ clinical records and analysed. In total, 85 patients (92.4% of eligible patients) had capacity to decide if they wanted the COVID-19 vaccine. Of these 68 (80.0%) consented and 17 (20.0%) declined to consent. A similar proportion of patients aged under and over 40 years old consented to have the vaccine. Those from a Black Asian minority ethnic background were more likely to decline the vaccine than White British patients. The reasons for capacitous refusal appeared similar to those seen in the general population.