We estimate the willingness to take the booster dose in a representative sample of Danes. We estimate an overall willingness in the adult Danish population of about 87 percent and a willingness of about 95.5 percent among primary vaccine takers. Moreover, we show that these percentages are significantly lower among younger populations, as well as among groups who do not see COVID-19 as a threat to society, those who do not feel that they have the ability to follow recommendations ('self-efficacy'), those who do not perceive the advice of the health authorities as effective against disease spread ('response efficacy'), and those who feel that the costs of following recommendations are high ('response cost').