INTRODUCTION. Based on survey data from September 2021, we recently reported that an estimated 90% (weighted total) of vaccinated (completed or scheduled) adult Danes were also willing to receive a COVID-19 booster vaccine, once offered. This survey was, however, fielded before booster vaccination was recommended to the general adult population in Denmark, which may have resulted in an underestimation of booster vaccine willingness. Therefore, we conducted a follow-up survey targeting the same individuals. METHODS. The follow-up survey wave was fielded in December 2021 using the same methods as in the September 2021 wave. Using data from participants responding to both survey waves, we compared COVID-19 booster vaccine willingness between the waves by means of paired t-test. RESULTS. A total of 1,429 invitees (58%) responded to the follow-up survey. Among those, 1,324 (93%) had also responded to the initial survey on COVID-19 booster vaccine willingness. At follow-up, among the 95% reporting to be vaccinated or that COVID-19 vaccination was scheduled, a weighted proportion of 95% indicated that they were willing to receive the booster vaccine once offered. Booster vaccine willingness at follow-up (December 2021) had statistically significantly increased (p < 0.001) compared with the initial survey (September 2021). CONCLUSIONS. Almost all of the COVID-19-vaccinated Danes seem willing to receive a booster dose of the vaccine, which bodes very well for the COVID-19 immunisation state in Denmark.